UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No.     )*

INDEPENDENT BANK GROUP, INC.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

45384B 106

(CUSIP Number)

David R. Brooks

1600 Redbud Boulevard, Suite 400

McKinney, Texas 75069

(972) 562-9004

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

April 3, 2013

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Sections 240.13d-1(e), (f) or (g), check the following box.   ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Section 240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

SCHEDULE 13D

Filed Pursuant to Rule 13d-1(a)

This Statement on Schedule 13D relates to the common stock, par value $0.01 per share (the “Common Stock”), of Independent Bank Group, Inc., a Texas corporation (the “Issuer”), and is being filed by David R. Brooks (the “Reporting Person”). The Issuer’s principal executive offices are located at 1600 Redbud Boulevard, Suite 400. McKinney, Texas 75069.

The Reporting Person is the beneficial owner of 1,075,568 shares of the Issuer’s Common Stock (the “Shares”), of which 1,039,498 shares of Common Stock are held directly by the Reporting Person, 12,800 are held by trusts established for the benefit of the Reporting Person’s children, of which the Reporting Person is the sole trustee of one of those trusts (6,400 shares), and 23,270 shares are represented by warrants that are currently exercisable by the Reporting Person.

The Reporting Person acquired (i) 137,846 of the Shares through restricted stock grants from the Issuer, of which 64,000 are unvested and subject to forfeiture as provided in the respective restricted stock agreement between the Issuer and the Reporting Person, (ii) 176,150 of the Shares as merger consideration in connection with the merger of Independent Bank Group Central Texas, Inc., a Texas corporation, with and into the Issuer and (iii) 738,302 of the Shares with personal funds and the proceeds of loans obtained by the Reporting Person from TIB - The Independent Bankersbank (the “Lender”). The Reporting Person’s obligations to the Lender are set forth in that certain Loan Agreement, effective December 15, 2008, between the Reporting Person and Lender, as modified by a Renewal, Extension, and Modification of Loan effective December 15, 2009, as further

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modified by a Renewal, Extension, and Modification of Loan effective January 25, 2011, and as further modified by a Renewal, Extension, and Modification of Loan effective January 25, 2012 (as amended or modified, the “Loan Agreement”), which Loan Agreement is supplemented by a Promissory Note dated December 15, 2008 (the “2008 Promissory Note”), in the principal amount (as amended) of $2,225,000, payable by the Reporting Person to the Lender, and a Pledge Agreement, dated December 15, 2008 between the Reporting Person and the Lender (the “2008 Pledge Agreement”) pursuant to which 962,093 of the Shares are pledged to secured the Reporting Person’s obligations under the Loan Agreement and the 2008 Promissory Note (the “Pledged Shares”). In addition, pursuant to a Promissory Note dated April 8, 2011 (the “2011 Promissory Note”), in the original principal amount of $300,000, the Reporting Person borrowed additional funds from the Lender, and entered into a Pledge Agreement, dated as of April 8, 2011, between the Reporting Person and the Lender (the “2011 Pledge Agreement”) pursuant to which the Pledged Shares are cross-pledged to the Lender to secure the Reporting Person’s obligations under the 2011 Promissory Note.

The remaining 23,270 of the Shares are represented by a Warrant held by the Reporting Person which is currently exercisable. To the extent exercised, the Reporting Person expects to use personal funds to fund the exercise price or effect the exercise of the warrant under the cashless exercise provisions thereof.

The shares of Common Stock beneficially owned by the Reporting Person were acquired by the Reporting Person for investment purposes. The Reporting Person intends to periodically review his investment in the Issuer and, based on a number of factors, including the Reporting Person’s evaluation of the Issuer’s business prospects and financial condition, the market for the Issuer’s shares, general economic and stock market conditions and other investment opportunities, the Reporting Person may acquire additional securities of the Issuer or dispose of the shares of Common Stock reported herein through open market or privately negotiated transactions.

The Reporting Person does not have any current plans or proposals which would relate to or would result in:

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The Reporting Person reserves the right to determine in the future to change the purpose or purposes described above.

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(1) The Reporting Person is party to the Loan Agreement, the 2008 Promissory Note, the 2008 Pledge Agreement, the 2011 Promissory Note and the 2011 Pledge Agreement pursuant to which the Reporting Person has pledged an aggregate of 962,093 of the Shares to secure the obligations of the Reporting Person to the Lender. The 2008 Pledge Agreement and the 2011 Pledge Agreement each provide for transfer of the voting and investment control over the Shares subject thereto upon the occurrence of certain events as more particularly set forth in such respective instrument. The descriptions of such Loan Agreement the 2008 Promissory Note, the 2008 Pledge Agreement, the 2011 Promissory Note and the 2011 Pledge Agreement, as applicable, are each qualified in their entirety by reference to the copy of such instruments attached hereto as Exhibit 1 (Loan Agreement), Exhibit 2 (2008 Promissory Note), Exhibit 3 (2008 Pledge Agreement), Exhibit 4 (2011 Promissory Note) and Exhibit 5 (2011 Pledge Agreement), respectively.

(2) The Reporting Person is party to a Letter Agreement, dated January 1, 2009, with the Issuer with respect to 38,400 shares of Common Stock acquired through restricted stock grants by the Issuer in favor of the Reporting Person under the Issuer’s 2005 Stock Plan. The Issuer’s 2005 Stock Plan provides for the vesting of the shares of Common Stock subject to such Letter Agreement, the escrow of the shares of Common Stock until vesting and provisions relating to the forfeiture of such shares of Common Stock upon the occurrence of certain event as more specifically set forth therein. The description of such Letter Agreement is qualified in its entirety by reference to the copy of such instrument attached hereto as Exhibit 6.

(3) The Reporting Person is party to a Restricted Stock Agreement, dated April 8, 2013, with the Issuer with respect to 25,600 shares of Common Stock acquired through a restricted stock grant by the Issuer in favor of the Reporting Person under the Issuer’s 2013 Stock Incentive Plan. Such Restricted Stock Agreement provides for the vesting of the shares of Common Stock subject thereto, the escrow of the shares of Common Stock until vesting and provisions relating to the forfeiture of such shares of Common Stock upon the occurrence of certain event as more specifically set forth therein. The description of such Restricted Stock Agreement is qualified in its entirety by reference to the copy of such instrument attached hereto as Exhibit 7.

(4) The Reporting Person is party to a Warrant Agreement, dated December 23, 2008, with the Issuer pursuant to which the Reporting Person has the right, but not the obligation, to purchase up to 23,270 shares of Common Stock at an exercise price of $17.1875 per share. Such Warrant Agreement has an expiration date of December 23, 2018 and is currently fully exercisable. The description of such Warrant Agreement is qualified in its entirety by reference to the copy of such instrument attached hereto as Exhibit 8.

(4) In connection with the Issuer’s initial public offering, the Reporting Person entered into a Lock-Up Agreement with Sandler O’Neill & Partners, L.P., the book-running manager for the offering, pursuant to which the Reporting Person agreed, among other things, not to offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant for the sale of, or otherwise dispose of or transfer any shares of the Issuer’s Common Stock or any securities convertible into or exchangeable or exercisable for shares of the Issuer’s Common Stock. The description of such Lock-Up Agreement is qualified in its entirety by reference to the copy of such instrument attached hereto as Exhibit 9.

(5) Other than as set forth above, the Reporting Person does not have any contract, arrangement, understanding or relationship with respect to securities of the Issuer, including, but not limited to, transfer or voting of any of the securities, finder’s fees, joint ventures, loan or option arrangements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies. Further, other than as set forth above, the Reporting Person has not pledged securities of the Issuer nor are the securities of the Issuer held by the Reporting Person subject to a contingency, the occurrence of which would give another person voting power or investment power over such securities.

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After reasonable inquiry, and to the best of the undersigned’s knowledge and belief, the undersigned certifies that the information set forth in this Statement on Schedule 13D is true, complete and correct.

Date: April 11, 2013

Attention: Intentional misstatements or

omissions of fact constitute Federal

criminal violations (See 18 U.S.C. § 1001).

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INDEX OF EXHIBITS

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Exhibit 1

TIB - THE INDEPENDENT BANKERSBANK

LOAN AGREEMENT

This Loan Agreement (“Agreement”) is made and entered into to be effective as of December 15, 2008, by and between TIB – THE INDEPENDENT BANKERSBANK (“Lender”) and DAVID BROOKS (“Borrower”).

WHEREAS, Borrower and Lender entered into that certain $1,106,655.00 loan transaction (as amended, modified, and increased, the “Existing Loan”), dated on or about December 28, 2004; and

WHEREAS, Borrower is or will be the owner of 291,000 shares (“Stock”) of the outstanding common stock of INDEPENDENT BANK GROUP, INC. (“IBG”), who is merging with Independent Bank Group Central Texas (“IBGCT”), and Borrower has applied to Lender for a loan (“Loan”) in an amount of up to $2,000,000.00, which loan will, in part, refinance the Existing Loan, plus provide Borrower with funds to purchase additional post-merger stock of IBG; and

WHEREAS, Borrower has, of even date herewith, executed and delivered to Lender a Promissory Note (“Note”) in the original stated principal amount of the Loan, which Note will pay off and replace the note evidencing the Existing Loan, and Borrower has executed and delivered that certain Pledge Agreement (“Pledge”) in favor of Lender, dated of even date herewith, covering the Stock, and various other Loan Documents (as defined below), as security for the Loan.

NOW THEREFORE, in connection with the Loan, and in consideration of Lender’s commitment to fund proceeds of the Loan, the parties hereby agree as follows:

1. Definitions. As used in this Agreement, the following terms shall have the following meanings:

“Average Assets” means, at any particular time, all amounts which, in conformity with GAAP, would be included as average assets on the balance sheet of Bank less (i) allowances for loan and lease losses, and (ii) goodwill and other intangible assets.

“Bank” means Independent Bank (McKinney).

“Classified Assets” means, at any particular time, all assets of IBG or Bank classified as “Loss,” “Doubtful,” or “Substandard” or in any equivalent category by IBG, Bank, or any governmental or regulatory authority.

“Equity Capital” means, at any particular time, the sum of Bank’s common capital stock, surplus (excluding surplus related to preferred stock), perpetual preferred stock and related surplus, and retained earnings, determined in accordance with GAAP, exclusive of allowances for loan and lease losses.

“Obligations” means all obligations, indebtedness, and liabilities of Borrower to Lender, now existing or hereafter arising, whether direct, indirect, related, unrelated, fixed, contingent, liquidated, unliquidated, joint, several, or joint and several, including, without limitation, the obligations, indebtedness, and liabilities of Borrower under this Agreement, the Note, and the other Loan Documents, and all interest accruing thereon and all attorneys’ fees and other expenses incurred in the enforcement or collection thereof.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 1

“Primary Capital” means the sum of Bank’s Equity Capital plus one hundred percent (100%) of its allowances for possible loan and lease losses.

“Return on Average Assets” means at any particular time for any specified period the ratio, expressed as a percentage, of Bank’s net income after taxes to Average Assets determined at the end of such period.

“Total Assets” means, at any particular time, all amounts which, in conformity with GAAP, would be included as assets on a balance sheet of Bank less (i) allowances for loan and lease losses, and (ii) goodwill and other intangible assets.

2. Conditions. Lender agrees to make and advance said Loan upon, and Borrower agrees to accept the Loan in accordance with, the provisions hereof and the other documents securing and evidencing the Loan (“Loan Documents”), and the Loan shall be advanced only upon and subject to the following conditions:

a. Borrower has fully complied with all the provisions of this Agreement and is otherwise entitled to such advance; and

b. The terms and conditions of the Note, Pledge, and other Loan Documents have been fully complied with and there is then no existing default (or event which, following the passage of time, or giving of notice, or both, would be a default thereunder).

3. Representations and Warranties. To induce Lender to enter into this Agreement, Borrower represents and warrants to Lender as follows:

(a) IBG (i) is a corporation or banking association duly organized, validly existing, and in good standing under the laws of its state of organization; (ii) has all requisite corporate power to own assets and carry on its business as now being or as proposed to be conducted; (iii) is qualified to do business in all jurisdictions in which the nature of its business makes such qualification necessary and where failure to so qualify would have a material adverse effect on its business, financial condition, or operations; and (iv) is authorized to issue the Stock. Borrower has the power and authority to execute, deliver, and perform its obligations under this Agreement and the other Loan Documents to which it is or may become a party.

(b) The borrowing hereunder and the execution, delivery and performance by Borrower of this Agreement, the Note, and the other Loan Documents have been duly authorized by all necessary action and are not in contravention of any law, rule or regulation or of the terms of any agreement or instrument to which Borrower is a party or by which it may be bound.

(c) This Agreement, the Note, and the other Loan Documents to which Borrower is a party, when delivered, shall constitute the legal, valid, and binding obligation of Borrower, enforceable against Borrower, in accordance with its respective terms, except as limited by bankruptcy, insolvency, or other laws of general application relating to the enforcement of creditors’ rights.

(d) Each financial statement of Borrower heretofore delivered to Lender was prepared in conformity with GAAP and truly disclosed Borrower’s financial condition (including all of Borrower’s contingent liabilities) as of the date thereof, and there has been no material adverse change in Borrower’s financial condition subsequent to the date of the most recent financial statement of Borrower delivered to Lender.

(e) No litigation or governmental proceeding is pending, or, to the knowledge of Borrower, threatened against or affecting Borrower, which may result in any material adverse change in Borrower’s business, properties or operations.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 2

(f) Borrower owns, and with respect to Collateral (as defined in the Pledge) acquired after the date hereof, Borrower will own, legally and beneficially, the Collateral free of any lien or claim or any right or option on the part of any third party to purchase or otherwise acquire the Collateral or any part thereof, except for any shareholder agreements between Borrower and Vincent Viola and the security interest granted to Lender pursuant to the Pledge and the Stock Power and Assignment. The Collateral is not subject to any restriction on transfer or assignment except for compliance with applicable federal and state securities laws and regulations promulgated thereunder. All of the Collateral has been duly and validly issued and is fully paid and nonassessable. Upon completion of the Merger, the authorized capital stock of IBG is 10,000,000 shares of common stock, par value $1.00 per share, of which 1,973,307 shares are issued and outstanding. All of the outstanding capital stock of IBG has been validly issued, is fully paid, and is non-assessable. The Stock will constitute 14.8% of the issued and outstanding shares of common capital stock of IBG. There are no existing subscriptions, options, warrants, calls, or rights (other than preemptive rights set forth in their respective articles of incorporation) to acquire, and no existing Debt, securities, or other instruments convertible into or exchangeable for, capital stock of IBG.

(g) No certificate or statement herewith or heretofore delivered by Borrower to Lender in connection herewith, or in connection with any transaction contemplated hereby, contains any untrue statement of a material fact or fails to state any material fact necessary to keep the statements contained therein from being misleading.

(h) No authorization, approval, or consent of, and no filing or registration with, any court, governmental authority, or third party is or will be necessary for the execution, delivery, or performance by Borrower of this Agreement and the other Loan Documents to which Borrower is or may become a party or the validity or enforceability thereof.

(i) Borrower is not in violation in any material respect of any law, rule, regulation, order, or decree of any court, governmental authority, or arbitrator or any agreement to which he is a party.

4. Affirmative Covenants. Borrower covenants and agrees that, as long as the Obligations or any part thereof are outstanding or Lender has any commitment hereunder, Borrower will observe and perform the following positive covenants, unless Lender shall otherwise consent in writing:

(a) Borrower will cause IBG to furnish to Lender as soon as available, and in any event within ninety (90) days after the end of each fiscal year, a copy of the annual audit report of IBG for such fiscal year containing, on a consolidated and unconsolidated basis, balance sheets, statements of income, statements of retained earnings, statements of changes in financial position, and cash flows as at the end of such fiscal year and for the 12-month period then ended, in each case setting forth in comparative form the figures for the preceding fiscal year, all in reasonable detail and audited and certified by independent certified public accountants of recognized standing acceptable to Lender, to the effect that such report has been prepared in accordance with GAAP.

(b) Borrower will promptly furnish to Lender, at Lender’s request and within Lender’s sole discretion, a certificate stating that to the best of Borrower’s knowledge, no Event of Default has occurred and is continuing, or if an Event of Default has occurred and is continuing, a statement as to the nature thereof and the action which is proposed to be taken with respect thereto, and showing in reasonable detail the calculations demonstrating compliance with Sections 5(d), 5(e), 5(f), and 5(h) hereof.

(c) Promptly, and in any event within ninety (90) days after each June 30 and December 31, Borrower will cause IBG to deliver to Lender a copy of a financial report of IBG for such period, prepared in conformity with GAAP, and which fairly and accurately states IBG’s financial condition at such time (including all assets, liabilities, contingent liabilities, and cash flow); such financial report shall include without limitation a copy of the most recent Federal Reserve Forms Y-9SP, Y-6, and/or Y-6A as sent to the Federal Reserve Bank of Dallas.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 3

(d) As soon as available, and in any event within forty-five (45) days after the anniversary date of the previous financial statement of Borrower delivered to Lender, Borrower will cause to be provided to Lender a copy of (i) an unaudited financial report of Borrower for the previous twelve (12) months, such report to include Borrower’s actual cash flow statement for such year, certified by Borrower, prepared in conformity with sound accounting principals consistently applied, and which fairly and accurately states Borrower’s financial condition (including all assets, liabilities, and contingent liabilities), (ii) a projected cash flow statement for Borrower for the forthcoming year, and (iii) a true and correct copy of Borrower’s tax return promptly upon filing of same with the Internal Revenue Service.

(e) Promptly, and in any event, prior to December 31 of each and every year during the term of the Loan (including renewals, modifications, and/or extensions thereof), Borrower shall and shall cause Bank to create and deliver to Lender a comprehensive and detailed fiscal budget for the forthcoming year, such budget to include projected cash flow information and a pro forma balance sheet.

(f) As soon as available, and in any event within sixty (60) days after the end of each fiscal quarter, Borrower will deliver to Lender copies of all Reports of Condition and Reports of Income of Bank as filed with the appropriate regulatory authorities.

(g) As soon as available, and in any event within thirty (30) days after the end of each calendar quarter, Borrower will furnish to Lender a report identifying the Classified Assets of Bank.

(h) As soon as available, Borrower will furnish to Lender one copy of each financial statement, report, notice, or proxy statement sent by IBG to its stockholders generally and one copy of each regular, periodic or special report, registration statement, or prospectus filed by IBG with any securities exchange or the Securities and Exchange Commission or any successor entity, and any material order issued by any court, governmental authority, or arbitrator in any proceeding to which either Borrower, IBG, or Bank is a party.

(i) As soon as available, and in any event within sixty (60) days after receipt by IBG, Borrower will furnish to Lender copies of the Uniform Bank Performance Report for Bank prepared by the Federal Financial Institutions Examination Council or any successor entity.

(j) Borrower will promptly inform Lender of any litigation against either Borrower, IBG, or Bank or affecting Borrower’s, IBG’s, or Bank’s property, if such litigation or potential litigation might, in the event of an unfavorable outcome, have a material adverse effect on Borrower’s, IBG’s , or Bank’s financial condition or might cause an Event of Default.

(k) Borrower will promptly furnish to Lender, at Lender’s request and within Lender’s sole discretion, such additional financial or other information concerning the assets, liabilities, operations and transactions of Borrower, IBG, or Bank as Lender may from time to time request.

(l) Borrower will promptly pay when due any and all taxes, assessments and governmental charges upon Borrower or against any of Borrower’s property, unless the same is being contested in good faith by appropriate proceedings and reserves deemed adequate by Lender have been established therefor.

(m) Borrower will cause IBG and Bank to maintain their existence and promptly comply with all laws, statutes, ordinances, governmental regulations, agreements, contracts, and instruments applicable to or binding upon them or to any of their property, business, operations and transactions.

(n) Borrower will cause IBG and Bank to maintain, with financially sound and reputable insurance companies or associations, insurance of the kinds, covering the risks and in the relative proportionate amounts, usually carried by companies engaged in businesses similar to that of IBG and Bank (such insurance to be in any event in such amounts and covering such risks as shall be satisfactory to Lender), and, at Lender’s request, deliver to Lender evidence of the maintenance of such insurance.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 4

(o) As soon as available, and in any event within thirty (30) calendar days after each meeting of the board of directors of IBG or Bank, Borrower will promptly deliver or cause to be delivered to Lender the directors’ report from such meeting including the minutes of such meeting and the monthly board package from such meeting.

(p) Borrower will cause Bank to maintain at all times a liquidity position determined by the ratio of total deposits to total loans which is in accordance with the guidelines recommended by applicable federal bank regulatory authorities and is deemed satisfactory at each regulatory examination of Bank.

(q) Borrower will cause Bank to maintain federal deposit insurance and to be a member of the Federal Deposit Insurance Corporation.

(r) Borrower will notify Lender, within five (5) days of the occurrence thereof, of the occurrence of an Event of Default or event which with the giving of notice or lapse of time or both would constitute an Event of Default.

(s) Borrower will permit and cause IBG and Bank to permit a representative of Lender to attend all meetings of the board of directors of IBG and Bank, whether regular meetings or specially called meetings.

(t) Borrower will promptly furnish to Lender written notice of (i) the issuance of any notice of charges, cease-and-desist order (temporary or otherwise) or order to take affirmative action by any governmental or regulatory authority against Borrower, IBG, or Bank or any director, officer, employee, agent, or other person participating in the conduct of the affairs of Borrower, IBG, or Bank, (ii) the service of any notice of intention to remove from office or notice of intention to suspend from office by any governmental or regulatory authority upon any director or officer of Borrower, IBG, or Bank, (iii) the issuance of a notice of termination of the status of Bank as an insured bank under the Federal Deposit Insurance Corporation Act, as amended, or (iv) the entry into any agreement or memorandum of understanding between any governmental or regulatory authority and Borrower, IBG, or Bank or any director, officer, employee, agent, or other person participating in the conduct of the affairs of IBG or Bank.

(u) Borrower shall maintain in good standing, by punctual payment of the premiums due thereon, key-man life insurance issued by a reputable insurance company on the life of Borrower in the minimum amount of $2,000,000.00, and on the life of Vincent Viola (“Viola”) in the minimum amount of $3,000,000.00 (the “Key-Man Policies”). The Key-Man Policies shall be assigned to Lender as security for the Obligations; provided that only $1,000,000.00 of Borrower’s policy shall secure the Obligations. In the event of the death of the insured, Borrower will give prompt notice thereof to Lender and Lender will have the right to apply the proceeds of the Key-Man Policies or any portion thereof to the prepayment of the Obligations, together with accrued interest thereon.

(v) If Lender in its sole discretion believes that it is advisable that the loan portfolio of Bank should be reviewed during any year during the term of the Loan, Borrower will provide or cause to be provided to Lender a third party loan review of Bank’s loan portfolio conducted by an independent third party acceptable to Lender, such review to begin within ninety (90) days after Lender’s written request therefor.

(w) Omitted

(x) Borrower shall cause Bank to maintain minimum Equity Capital of $60,000,000.00, to be analyzed on a quarterly basis.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 5

(y) Borrower shall cause Bank to be Well Capitalized (as defined by the FDIC), including maintaining a minimum Total Risk Based Capital Ratio (Tier 1 and Tier 2 Capital divided by risk-weighted assets) equal to or greater than ten percent (10%) or such greater percentage as may be required by applicable regulatory authorities, to be tracked on a quarterly basis.

5. Negative Covenants. Borrower covenants and agrees that, as long as the Obligations or any part thereof are outstanding or Lender has any commitment hereunder, Borrower will perform and observe the following negative covenants, unless Lender shall otherwise consent in writing:

(a) Borrower will not permit to occur any material adverse changes in his financial position nor make any loans or investments that would materially and negatively affect his net worth without Lender’s prior written consent;

(b) Following the Merger, Borrower will not permit IGB or Bank to reorganize, merge, or consolidate with, or acquire all or substantially all of the assets of, any other company, firm or association, or make any other substantial change in their respective capitalization or character of its business.

(c) Borrower will not permit IBG or Bank to sell, lease, or otherwise dispose of any of its assets used or useful in its business, except in the regular course of business for reasonably equivalent consideration;

(d) Borrower will not permit the Classified Assets of Bank to at any time exceed fifty percent (50%) of the Primary Capital of Bank;

(e) Borrower will not permit the ratio of Bank’s Equity Capital to its Total Assets to at any time be less than the greater of six and one-half percent (6.5%) or such greater percent as may be required by applicable regulatory authorities, to be tracked on a quarterly basis.

(f) Borrower will not permit IBG or Bank to enter into any speculative activities or securities hedging;

(g) Borrower will not permit Bank’s Return on Average Assets to be less than 1.00%, calculated quarterly:

(h) Borrower will not permit IBG or Bank to make any change in accounting treatment or reporting practices, except as required by GAAP; and

(i) Borrower will not consent to or vote in favor of or take any action to support the granting of a security interest in the stock of IBG or Bank without Lender’s prior written consent.

6. An “Event of Default” as used in this Agreement or any other of the Loan Documents shall mean the occurrence of any of the following events:

a. the failure of Borrower to make due and punctual payment of the Note or of any other secured indebtedness or of any installment of principal thereof or interest thereon, or of any other amount required to be paid under the Note or the Pledge, as the same shall become due and payable, whether at maturity or when accelerated pursuant to any power to accelerate contained in the Note or contained herein and such failure shall continue for five (5) days after written notice from Lender to Borrower; or

b. the failure of Borrower to timely and properly observe, keep or perform any covenant, agreement, warranty or condition herein required to be observed, kept or performed if such failure continues for twenty (20) days after Borrower is notified thereof; or

LOAN AGREEMENT – Brooks - $2,000,000 – Page 6

c. without the prior written consent of the Lender, Borrower sells, exchanges, assigns, transfers, conveys or otherwise disposes of all or any part of the Stock or any interest therein, or legal or equitable title to the Stock or any interest therein is vested in any other party, in any manner whatsoever, by operation of law or otherwise, it being understood that the consent of the Lender required hereunder may be refused by the Lender in its sole discretion or may be predicated upon any terms, conditions and covenants deemed advisable or necessary in the sole discretion of the Lender, including but not limited to the right to change the interest rate, date of maturity or payments of principal or interest on the Note, to require payment of any amount as additional consideration as a transfer fee or otherwise and to require assumption of the Note and the Pledge; or

d. This Agreement or any other Loan Document shall cease to be in full force and effect or shall be declared null and void or the validity or enforceability thereof shall be contested or challenged by Borrower, or Borrower shall deny that it has any further liability or obligation under any of the Loan Documents.

e. Borrower shall fail, at any time, to own and have pledged to Lender at least the percentage of the issued and outstanding shares of common capital stock of IBG stated in Section 3(f), above, or such security interest in favor of Lender shall at any time fail to be a first priority perfected lien and security interest.

f. The Stock shall be subject to a security interest other than security interests in favor of Lender.

g. a default occurs under any other agreements or instruments evidencing or relating to the Obligations; or

h. the failure of Borrower to maintain its existence and authority to do business, if Borrower is an entity; or

i. the death or insolvency of Borrower, if applicable, or of a guarantor, if any, of the secured indebtedness; or

j. any representation contained herein or in the Pledge Agreement is false or misleading in any material respect; or

k. Lender in good faith deems itself insecure and/or reasonably determines that the prospect of Loan repayment is in question.

l. the failure of IBG to merge with IBGCT on or before January 6, 2009, or the failure of Borrower to deliver additional shares of common stock received by Borrower in such merger to Lender prior to January 6, 2009.

7. Borrower agrees to pay to Lender the reasonable attorney’s fees and expenses of Lender’s counsel, and any actual expenses incurred by the Lender in connection with the consummation of the transactions contemplated by this Loan Agreement.

8. This Agreement is made for the sole protection and benefit of Borrower and of Lender and no other person or persons shall be deemed to have any privity of contract hereunder nor any right of action of any kind hereon.

9. No waiver by Lender of any breach of any covenant of Borrower herein contained shall be construed as a waiver of any subsequent breach of the same or any other covenant herein contained.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 7

10. This Agreement shall be binding upon and shall inure to the benefit of each of the parties hereto and their respective successors and assigns in the event said party is a corporation or other legal entity, and said party’s respective heirs, executors and personal representatives in the event said party is an individual.

11. The terms and conditions of this Agreement shall be construed pursuant to and in accordance with laws of the State of Texas and all of the covenants and obligations hereunder are fully enforceable and performable in Dallas County, Texas.

IN WITNESS WHEREOF, this Agreement was executed to be effective as of the date first written above.

LOAN AGREEMENT – Brooks - $2,000,000 – Page 8

TIB – The Independent BankersBank

RENEWAL, EXTENSION, AND MODIFICATION OF LOAN

(David R. Brooks)

THIS MODIFICATION OF LOAN (this “Modification”) is made by and between DAVID R. BROOKS (“Borrower”) and TIB–THE INDEPENDENT BANKERSBANK (“Lender”), to be effective as of the 15th day of December, 2009.

RECITALS:

WHEREAS, Borrower executed and delivered to Lender that certain Promissory Note, dated December 15, 2008, in the stated principal amount of Two Million and No/100 Dollars ($2,000,000.00) (the “Note”); and

WHEREAS, as partial security for the Note, Borrower delivered to Lender that certain Pledge Agreement (the “Pledge Agreement”), dated of even date with the Note, pledging Borrower’s stock (the “Stock”) in Independent Bank Group, Inc. (“IBG”); and

WHEREAS, as additional security for the Note, Borrower delivered to Lender an Assignment of Life Insurance Policy on Policy No. 48140365, insuring Borrower in the face amount of $2,000,000.00, issued by New York Life Insurance Company (but limited as provided therein); and

WHEREAS, to further evidence the loan (“Loan”) evidenced by the Note, Borrower and Lender executed that certain Loan Agreement (the “Loan Agreement”) of even date with the Note and Pledge Agreement; and

WHEREAS, all obligations and indebtedness now existing or hereafter from time to time owing to the Lender under the Note, Pledge Agreement, Loan Agreement, or other documents which have been executed by Borrower from time to time to secure or evidence the Note (as hereby renewed, modified, and extended) are sometimes collectively referred to herein as the “Obligations” (and the Note, Pledge Agreement, Loan Agreement, and all documents evidencing the Loan described therein are herein collectively, the “Loan Documents”); and

WHEREAS, Borrower desires to increase the amount of the loan to allow him to purchase more Stock, and to otherwise modify the terms of the Obligations, and Lender agrees to such increase and modification pursuant to the terms hereof.

AGREEMENTS:

NOW, THEREFORE, for and in consideration of the mutual covenants and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereby agree as follows:

MODIFICATION OF LOAN – Brooks.12.09 – Page 1

295,550 shares of the outstanding Common Stock of Independent Bank Group, Inc. (“IBG”).

Further, Borrower agrees to deliver certificates representing the New Shares and blank stock powers therefor to Lender within twenty-one (21) days of the date hereof. Additionally, the terms of that certain Letter of Agreement (the “Agreement”), dated effective January 1, 2009, between Lender and Borrower, wherein Borrower agrees to deliver certain Restricted Shares (as defined therein) to Lender, shall continue to apply. Following delivery of the New Shares, Lender will have 272,473 shares of stock in its possession, with the remainder of the Collateral to be delivered to Lender in accordance with the terms of the Agreement.

MODIFICATION OF LOAN – Brooks.12.09 – Page 2

THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN BORROWER AND LENDER.

Executed to be effective as of the effective date first written above.

The foregoing instrument was acknowledged before me this 11th day of December, 2009, by DAVID R. BROOKS.

The foregoing instrument was acknowledged before me on the 15th day of December, 2009, by J. RICK JAMIESON, Senior Vice President of TIB – THE INDEPENDENT BANKERSBANK, on behalf of said bank.

MODIFICATION OF LOAN – Brooks.12.09 – Page 3

TIB – The Independent BankersBank

RENEWAL, EXTENSION, AND MODIFICATION OF LOAN

(David R. Brooks)

THIS RENEWAL, EXTENSION, AND MODIFICATION OF LOAN (this “Modification”) is made by and between DAVID R. BROOKS (“Borrower”) and TIB—THE INDEPENDENT BANKERSBANK (“Lender”), to be effective as of the 25th day of January, 2011.

RECITALS:

WHEREAS, Borrower executed and delivered to Lender that certain Promissory Note, dated December 15, 2008, in the stated principal amount of Two Million and No/100 Dollars ($2,000,000.00) (as previously renewed, extended, and modified, the “Note”); and

WHEREAS, as partial security for the Note, Borrower delivered to Lender that certain Pledge Agreement (as previously renewed, extended, and modified, the “Pledge Agreement”), dated of even date with the Note, pledging Borrower’s stock (the “Stock”) in Independent Bank Group, Inc. (“IBG”); and

WHEREAS, as additional security for the Note, Borrower delivered to Lender an Assignment of Life Insurance Policy on Policy No. 48140365, insuring Borrower in the face amount of $2,000,000.00, issued by New York Life Insurance Company (but limited as provided therein); and

WHEREAS, to further evidence the loan (“Loan”) evidenced by the Note, Borrower and Lender executed that certain Loan Agreement (the “Loan Agreement”) of even date with the Note and Pledge Agreement; and

WHEREAS, all obligations and indebtedness now existing or hereafter from time to time owing to the Lender under the Note, Pledge Agreement, Loan Agreement, or other documents which have been executed by Borrower from time to time to secure or evidence the Note (as heretofore and hereby renewed, extended, and modified) are sometimes collectively referred to herein as the “Obligations” (and the Note, Pledge Agreement, Loan Agreement, and all documents evidencing the Loan described therein are herein collectively, the “Loan Documents”); and

WHEREAS, Borrower desires to modify the terms of the Loan and extend the time for Borrower’s performance of the Obligations, and Lender agrees to such modification and extension pursuant to the terms hereof.

AGREEMENTS:

NOW, THEREFORE, for and in consideration of the mutual covenants and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereby agree as follows:

Borrower shall cause Bank to maintain minimum Equity Capital of $90,000,000.00, to be analyzed on a quarterly basis.

THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN BORROWER AND LENDER.

[SIGNATURE PAGE FOLLOWS]

Executed to be effective as of the effective date first written above.

The foregoing instrument was acknowledged before me this 26th day of January, 2011, by DAVID R. BROOKS.

The foregoing instrument was acknowledged before me on the 26th day of January, 2011, by TANDY L. HIX, Senior Vice President of TIB–THE INDEPENDENT BANKERSBANK, on behalf of said bank.

TIB – The Independent BankersBank

RENEWAL, EXTENSION, AND MODIFICATION OF LOAN

(David R. Brooks)

THIS RENEWAL, EXTENSION, AND MODIFICATION OF LOAN (this “Modification”) is made by and between DAVID R. BROOKS (“Borrower”) and TIB—THE INDEPENDENT BANKERSBANK (“Lender”), to be effective as of the 25^th day of January, 2012.

RECITALS:

WHEREAS, Borrower executed and delivered to Lender that certain Promissory Note, dated December 15, 2008, in the stated principal amount of Two Million and No/100 Dollars ($2,000,000.00) (as previously renewed, extended, and modified, the “Note”); and

WHEREAS, as partial security for the Note, Borrower delivered to Lender that certain Pledge Agreement (as previously renewed, extended, and modified, the “Pledge Agreement”), dated of even date with the Note, pledging Borrower’s stock (the “Stock”) in Independent Bank Group, Inc. (“IBG”); and

WHEREAS, as additional security for the Note, Borrower delivered to Lender an Assignment of Life Insurance Policy on Policy No. 48140365, insuring Borrower in the face amount of $2,000,000.00, issued by New York Life Insurance Company (but limited as provided therein); and

WHEREAS, to further evidence the loan (“Loan”) evidenced by the Note, Borrower and Lender executed that certain Loan Agreement (the “Loan Agreement”) of even date with the Note and Pledge Agreement; and

WHEREAS, all obligations and indebtedness now existing or hereafter from time to time owing to the Lender under the Note, Pledge Agreement, Loan Agreement, or other documents which have been executed by Borrower from time to time to secure or evidence the Note (as heretofore and hereby renewed, extended, and modified) are sometimes collectively referred to herein as the “Obligations” (and the Note, Pledge Agreement, Loan Agreement, and all documents evidencing the Loan described therein are herein collectively, the “Loan Documents”); and

WHEREAS, Borrower desires to modify the terms of the Loan and extend the time for Borrower’s performance of the Obligations, and Lender agrees to such modification and extension pursuant to the terms hereof.

AGREEMENTS:

NOW, THEREFORE, for and in consideration of the mutual covenants and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereby agree as follows:

MODIFICATION OF LOAN — Brooks — Page 1

Borrower shall cause Bank to maintain minimum Tangible Equity Capital (defined as Equity Capital [as defined in this Loan Agreement] less intangible assets) of $90,000,000.00, to be analyzed on a quarterly basis.

MODIFICATION OF LOAN — Brooks — Page 2

THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN BORROWER AND LENDER.

[SIGNATURE PAGE FOLLOWS]

MODIFICATION OF LOAN — Brooks — Page 3

Executed to be effective as of the effective date first written above.

The foregoing instrument was acknowledged before me this 12th day of March, 2012, by DAVID R. BROOKS.

The foregoing instrument was acknowledged before me on the             day of March, 2012, by TANDY L. HIX, Senior Vice President of TIB – THE INDEPENDENT BANKERSBANK, on behalf of said bank.

MODIFICATION OF LOAN — Brooks — Page 4

Exhibit 2

TIB - THE INDEPENDENT BANKERSBANK

PROMISSORY NOTE

FOR VALUE RECEIVED, the undersigned, DAVID BROOKS (“Maker”), promises to pay to the order of TIB — THE INDEPENDENT BANKERSBANK (“Payee”) the principal sum of Two Million and No/100 Dollars ($2,000,000.00), or so much thereof as shall be advanced hereunder, at or before the maturity of this Note, with interest on the unpaid balance outstanding from time to time at the rate or rates specified below, both principal and interest payable as provided below in lawful money of the United States of America at the address of Payee set forth below or at such other place as from time to time may be designated by the holder of this Note.

I. Interest Rates and Payments

Prior to default or maturity, the unpaid principal of this Note from time to time outstanding shall bear interest at the rate (“Rate”) of interest per annum equal to the greater of (i) four percent (4%) (the “Floor”) or (ii) the rate reported in the Credit Markets section (or similar section) of The Wall Street Journal as the U.S. “Prime Rate”, as announced from time to time automatically fluctuating upward and downward with each announcement without notice to Maker or any other person (the “Index”), provided that in no event shall the Rate exceed the maximum interest rate permitted under applicable law (“Maximum Rate”). If hereafter the Index shall change, the rate of interest on the unpaid balance of principal of this Note prior to maturity shall be increased or decreased, as the case may be, from time to time as of the effective date of each change in the Index (but in no event less than the Floor). If applicable law provides for a ceiling, that ceiling shall be the indicated rate ceiling. All interest accruing under this Note shall be calculated on the basis of a 360-day year applied to the actual number of days elapsed.

Payments of principal in an amount necessary to amortize the stated principal hereof over a 120- month period, plus accrued and unpaid interest, shall be due and payable commencing on April 25, 2009 and continuing on each April 25, July 25, October 25, and January 25 thereafter until and including December 15, 2013, on which date all accrued interest, principal (which will be a balloon payment), and other charges under this Note shall be fully due and payable.

All principal and interest which is matured or otherwise past due under this Note shall bear interest at the Maximum Rate, or, if no such rate is designated under applicable law, at the rate of eighteen percent (18%) per annum.

This Note may be advanced in one or more advances. Advances shall be made in accordance with the Loan Agreement of even date herewith between Maker and Payee, provided that no amounts borrowed and repaid hereunder may be re-borrowed. Maker shall have the right to prepay, without penalty, at any time and from time to time prior to maturity, all or any part of the unpaid principal balance of this Note and all or any part of the unpaid interest accrued to the date of such prepayment, provided that any such principal thus paid is accompanied by accrued interest on such principal. Any partial prepayments of principal shall be applied to installments thereof in the inverse order of maturity.

PROMISSORY NOTE — Brooks - $2,000,000 - Page 1

II. Security

This Note is secured by, Inter alia, a Pledge Agreement (the “Pledge Agreement”) of even date herewith from Maker to Payee, to which Pledge Agreement reference is made for a description of the property covered thereby and the nature and extent of the rights and powers of the holder of this Note in respect of such property.

III. Right to Accelerate Upon Default

The holder of this Note shall have the option of declaring the principal balance hereof and the interest accrued hereon to be immediately due and payable upon the failure of Maker to pay any installment of the principal of or interest on this Note when due and such failure shall continue for a period of five (5) days after notice from Payee to Maker, or upon the occurrence of a default specified in the Pledge Agreement or in any other document securing or evidencing the obligations established by this Note (this Note, the Pledge Agreement, and any such other documents are called the “Loan Documents” below), and the continuance of such default for a relevant grace or notice period provided therein.

IV. Waiver of Conditions and Defenses to Liability

Maker and any other party who is or becomes liable to pay all or any part of this Note, or who grants any lien or security interest to secure all or any part of this Note (each called an “other liable party” below), including but not limited to any drawer, acceptor, endorser, guarantor, surety or accommodation party, severally waive presentment for payment, demand, notice of demand and of dishonor and nonpayment of this Note, notice of intention to accelerate the maturity of this Note, protest and notice of protest, diligence in collecting, and the bringing of suit against any other party.

Further, Maker and any other liable party severally waive any notice of or defense based upon any agreement or consent of the holder of this Note made or given from time to time, before or after maturity, to any of the following: the acceleration, renewal or extension of this Note; a change in the time or manner of payments required by this Note; a change in the rates of interest specified in this Note; acceptance or surrender of security; a substitution of security or subordination, amendment or release of security; an addition or release of any other liable party; changes of any sort whatever in the terms of payment of this Note or in the manner of doing business with Maker; and any settlement or compromise with Maker or any other liable party on such terms as the holder of this Note may deem appropriate in its sole and absolute discretion.

The holder of this Note may apply all moneys received from Maker or others, or from any security (whether held under a security instrument or not), in such manner upon the indebtedness evidenced or secured by any Loan Documents (whether then due or not) as such holder may determine to be in its best interest, without in any way being required to marshal assets or to apply all or any part of such moneys upon any particular part of such indebtedness. The holder of this Note is not required to retain, hold, protect, exercise due care with respect to, perfect security interests in or otherwise assure or safeguard any security for this Note, and no failure by the holder of this Note to do any of the foregoing and no exercise or failure to exercise by such holder of any other right or remedy shall in any way affect any of Maker’s or any other liable party’s obligations hereunder or under other Loan Documents or affect any security or give Maker or any other liable party any recourse against the holder of this Note.

PROMISSORY NOTE — Brooks - $2,000,000 - Page 2

V. Usury Savings Provision

It is the intent of Maker and Payee in the execution of this Note and all other Loan Documents to contract in strict compliance with applicable usury law. In furtherance thereof, Maker and Payee stipulate and agree that none of the terms and provisions contained in this Note, or in any other instrument executed in connection herewith, shall ever be construed to create a contract to pay for the use, forbearance or detention of money, interest at a rate in excess of the Maximum Rate. Neither Maker nor any guarantors, endorsers or other parties now or hereafter becoming liable for payment of this Note shall ever be obligated or required to pay interest on this Note at a rate in excess of the Maximum Rate, and the provisions of this paragraph shall control over all other provisions of this Note and any other Loan Documents now or hereafter executed which may be in apparent conflict herewith. Payee expressly disavows any intention to charge or collect excessive unearned interest or finance charges in the event the maturity of this Note is accelerated. If the maturity of this Note shall be accelerated for any reason or if the principal of this Note is paid prior to the end of the term of this Note, and as a result thereof the interest received for the actual period of existence of the loan evidenced by this Note exceeds the applicable maximum lawful rate, the holder of this Note shall credit the amount of such excess against the principal balance of this Note then outstanding and thereby shall render inapplicable any and all penalties of any kind provided by applicable law as a result of such excess interest; provided, however, that if the principal hereof has been paid in full, such excess shall be refunded to Maker. If the holder of this Note shall receive money (or anything else) which is determined to constitute interest and which would increase the effective interest rate on this Note or the other indebtedness secured by the Loan Documents to a rate in excess of that permitted by applicable law, the amount determined to constitute interest in excess of the lawful rate shall be credited against the principal balance of this Note then outstanding or, if the principal balance has been paid in full, refunded to Maker, in which event any and all penalties of any kind under applicable law as a result of such excess interest shall be inapplicable. If the holder of this Note shall not actually receive, but shall contract for, request or demand, a payment of money (or anything else) which is determined to constitute interest and which would increase the effective interest rate contracted for or charged on this Note or the other indebtedness evidenced or secured by the Loan Documents to a rate in excess of that permitted by applicable law, the holder of this Note shall be entitled, following such determination, to waive or rescind the contractual claim, request or demand for the amount determined to constitute interest in excess of the lawful rate, in which event any and all penalties of any kind under applicable law as a result of such excess interest shall be inapplicable. By execution of this Note Maker acknowledges that Maker believes the loan evidenced by this Note to be non-usurious and agrees that if, at any time, Maker should have reason to believe that such loan is in fact usurious, Maker will give the holder of this Note notice of such condition and Maker agrees that the holder shall have sixty (60) days in which to make appropriate refund or other adjustment in order to correct such condition if in fact such exists. Additionally, if, from any circumstance whatsoever, fulfillment of any provision hereof or any other Loan Documents shall, at the time fulfillment of such provision be due, involve transcending the Maximum Rate then, ipso facto, the obligation to be fulfilled shall be reduced to the Maximum Rate. The term “applicable law” as used in this Note shall mean the laws of the State of Texas or the laws of the United States, whichever laws allow the greater rate of interest, as such laws now exist or may be changed or amended or come into effect in the future.

VI. Miscellaneous

Should the indebtedness represented by this Note or any part thereof be collected at law or in equity or through any bankruptcy, receivership, probate or other court proceedings or if this Note is placed in the hands of attorneys for collection after default, Maker and all endorsers, guarantors and sureties of this Note jointly and severally agree to pay to the holder of this Note in addition to the principal and interest due and payable hereon all the costs and expenses of the holder in enforcing this Note including, without limitation, reasonable attorneys’ fees and legal expenses.

PROMISSORY NOTE — Brooks - $2,000,000 - Page 3

This Note and the rights, duties and liabilities of the parties hereunder or arising from or relating in any way to the indebtedness evidenced by this Note or the transaction of which such indebtedness is a part shall be governed by and construed in accordance with the law of the State of Texas and the law of the United States applicable to transactions within such State.

No amendment of this Note shall be binding unless expressed in a writing executed by Maker and the holder of this Note.

Maker certifies, represents, and warrants to Payee that the proceeds hereof are to be used for a commercial purpose and not for personal, family, household, or agricultural purposes.

MAKER IRREVOCABLY SUBMITS TO THE NON-EXCLUSIVE JURISDICTION OF ANY TEXAS OR FEDERAL COURT SITTING IN DALLAS COUNTY, TEXAS OVER ANY SUIT, ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO ANY OF THE LOAN DOCUMENTS, AND MAKER HEREBY AGREES AND CONSENTS THAT, IN ADDITION TO ANY METHODS OF SERVICE OF PROCESS PROVIDED FOR UNDER APPLICABLE LAW, ALL SERVICE OF PROCESS IN ANY SUCH SUIT, ACTION OR PROCEEDING IN ANY TEXAS OR FEDERAL COURT SITTING IN DALLAS COUNTY, TEXAS (OR SUCH OTHER COUNTY IN TEXAS) MAY BE MADE BY CERTIFIED OR REGISTERED MAIL, RETURN RECEIPT REQUESTED, DIRECTED TO MAKER AT THE ADDRESS INDICATED BELOW, AND SERVICE SO MADE SHALL BE COMPLETE FIVE DAYS AFTER THE SAME SHALL HAVE BEEN SO MAILED.

Payee’s Address:

TIE—THE INDEPENDENT BANKERSBANK

P. O. Box 560528

Dallas, TX 75356-0528

PROMISSORY NOTE — Brooks - $2,000,000 - Page 4

Exhibit 3

A. Security Interest. For good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, Pledgor/Debtor (hereinafter referred to as “Pledgor,” whether one or more) pledges, assigns and grants to Bank a security interest and lien in the Collateral (hereinafter defined) to secure the payment and the performance of the Obligations (hereinafter defined).

B. Collateral. The security interest is granted in the following collateral (the “Collateral”):

1. 291,000 shares of the outstanding Common Stock of Independent Bank Group, Inc. (“IBG”), a portion of which shall be delivered to Bank promptly upon the merger of IBG and Independent Bank Group Central Texas, in accordance with the Trust Receipt of even date herewith.

2. Reserved.

3. All additions, substitutes and replacements for and proceeds of the above Collateral (including all income and benefits resulting from any of the above, such as dividends payable or distributable in cash, property or stock; interest, premium and principal payments; redemption proceeds and subscription rights; and shares or other proceeds of conversions or splits of any securities in the Collateral). Notwithstanding the foregoing, so long as no Event of Default has occurred and is continuing, but only if at all times the Tangible Book Value of IBG is at least $32,000,000.00, the Bank agrees that Pledgor may receive dividends on the Collateral. As used above, Tangible Book Value is defined as Total Equity Capital (as defined in the Loan Agreement) plus loan loss reserve minus intangibles.

4. The balance of every deposit account of Pledgor maintained with Bank and any other claim of Pledgor against Bank, now or hereafter existing, liquidated or unliquidated, and all money, instruments, investment property, securities, documents, chattel paper, credits, claims, demands, income, and any other property, rights and interests of Pledgor which at any time shall come into the possession or custody or under the control of Bank or any of its agents or affiliates, for any purpose, and the proceeds of any thereof. Bank shall be deemed to have possession of any of the Collateral in transit to or set apart for it or any of its agents or affiliates.

PLEDGE AGREEMENT – Brooks - $2,000,000 – Page 1

C. Obligations.

1. Description of Obligations. The following obligations (“Obligations”) are secured by this Agreement: (a) all debts, obligations, liabilities and agreements of DAVID BROOKS (“Borrower”), to Bank, now or hereafter existing, arising directly or indirectly between Borrower and Bank whether absolute or contingent, joint or several, secured or unsecured, due or not due, contractual or tortious, liquidated or unliquidated, arising by operation of law or otherwise, and all renewals, extensions or rearrangement of any of the above; (b) all costs incurred by Bank to obtain, preserve, perfect and enforce this Agreement and maintain, preserve, collect and enforce the Collateral; (c) all debts, obligations, liabilities and agreements of Pledgor to Bank under this Agreement; (d) interest on the above amounts determined in accordance with applicable agreements between Bank and Pledgor or between Bank and Borrower; (e) all indebtedness, liabilities and obligations of Borrower to Bank under the Loan Agreement dated even date hereof (the “Loan Agreement”) between Borrower and Bank and all renewals, extensions and modifications thereof; (f) all indebtedness, liabilities and obligations of Borrower to Bank under the Promissory Note dated the date hereof (the “Note”) in the stated principal amount of $2,000,000.00 payable by Borrower to the order of Bank and all renewals, extensions and modifications thereof; and (g) all reasonable expenses of the Bank, including reasonable fees and expenses of the Bank’s counsel, incident to the enforcement of payment of all obligations of the Pledgor by any action or participation in, or in connection with a case or proceeding under the Bankruptcy Code, or any successor statute thereto.

In the event any amount paid to Bank on any of the Obligations is subsequently recovered from Bank in or as a result of any bankruptcy, insolvency or fraudulent conveyance proceeding involving an obligor of the Obligations other than Pledgor, Pledgor shall be liable to Bank for the amounts so recovered up to the fair market value of the Collateral whether or not the Collateral has been released or the security interest terminated. In the event the Collateral has been released or the security interest terminated, the fair market value of the Collateral shall be determined, at Bank’s option, as of the date the Collateral was released, the security interest terminated, or said amounts were recovered.

2. Use of Proceeds. The proceeds of any indebtedness or obligation secured by the Collateral will not be used directly or indirectly to purchase or carry any “margin stock” as that term is defined in Regulation U of the Board of Governors of the Federal Reserve System, or extend credit to or invest in other parties for the purpose of purchasing or carrying any such “margin stock,” or to reduce or retire any indebtedness incurred for such purpose or otherwise in a manner which would violate Regulations T or U.

D. Pledgor’s Warranties. Pledgor hereby represents and warrants to Bank as follows:

1. Financing Statements. Except as may be noted by schedule attached hereto and incorporated herein by reference, no financing statement covering the Collateral is or will be on file in any public office, except the financing statements relating to this security interest, and no security interest, other than the one herein created, has attached or been perfected in the Collateral or any part thereof.

2. Ownership. Pledgor owns, or will use the proceeds of any loans by Bank to become the owner of, the Collateral free from any setoff, claim, restriction, lien, security interest or encumbrance except liens for taxes not yet due and payable and the security interest hereunder.

3. Power and Authority. Pledgor has full power and authority to make this Agreement, and all necessary consents and approvals of any persons, entities, governmental or regulatory authorities and securities exchanges have been obtained to effectuate the validity of this Agreement.

E. Pledgor’s Covenants. Until full payment and performance of all of the Obligations and termination or expiration of any obligation or commitment of Bank to make advances or loans to Borrower, unless Bank otherwise consents in writing:

1. Obligations and This Agreement. Pledgor shall perform all of its agreements herein and in any other agreements between it and Bank.

2. Ownership of and Rights in Collateral. Pledgor shall defend the Collateral against all claims and demands of all persons at any time claiming any interest therein adverse to Bank. Pledgor shall keep the Collateral free from all liens and security interests except those for taxes not yet due and payable and the security interest hereby created. Any investment property and/or securities received by Pledgor, which shall comprise

PLEDGE AGREEMENT – Brooks - $2,000,000 – Page 2

additions, substitutes and replacements for, or proceeds of, the Collateral, shall be held in trust for Bank and shall be delivered immediately to Bank. Any cash proceeds from the Collateral shall be held in trust for Bank and upon demand shall be delivered immediately to Bank.

3. Bank’s Costs. Pledgor shall pay all costs necessary to obtain, preserve, perfect, defend and enforce the security interest created by this Agreement, collect the Obligations, and preserve, defend, enforce and collect the Collateral, including but not limited to taxes, assessments, reasonable attorney’s fees, legal expenses and expenses of sales. Whether the Collateral is or is not in Bank’s possession, and without any obligation to do so and without waiving Pledgor’s default for failure to make any such payment, Bank at its option may pay any such costs and expenses and discharge encumbrances on the Collateral, and such payments shall be a part of the Obligations and bear interest at the rate set out in the Obligations. Pledgor agrees to reimburse Bank on demand for any costs so incurred.

4. Information and Inspection. Pledgor shall (i) promptly furnish Bank any information with respect to the Collateral reasonably requested by Bank; (ii) allow Bank or its representatives to inspect and copy, or furnish Bank or its representatives with copies of, all records relating to the Collateral and the Obligations; and (iii) promptly furnish Bank or its representatives with any other information Bank may reasonably request.

5. Additional Documents. Pledgor shall sign and deliver any papers furnished by Bank which are necessary or desirable in the judgment of Bank to obtain, maintain and perfect the security interest hereunder and to enable Bank to comply with any federal or state law in order to obtain or perfect Bank’s interest in the Collateral or to obtain proceeds of the Collateral.

6. Notice of Changes. Pledgor shall notify Bank immediately of (i) any material change in the Collateral, (ii) a change in Pledgor’s residence or location, (iii) a change in any matter warranted or represented by Pledgor in this Agreement, or in any of the loan documents relating to the Obligations or furnished to Bank pursuant to this Agreement, and (iv) the occurrence of an Event of Default as defined herein.

7. Possession of Collateral. Pledgor shall deliver a copy of this Agreement (or other notice acceptable to Bank) to any Broker, financial intermediary, or any other person in possession of any of the Collateral or on whose books the interest of Pledgor in the Collateral appears, and such delivery shall constitute notice to such person of Bank’s security interest in the Collateral and shall constitute Pledgor’s instruction to such person to note Bank’s security interest on their books and records, or deliver to Bank certificates or other evidence of the Collateral promptly upon Bank’s request. Pledgor shall deliver all investment securities and other instruments and documents which are a part of the Collateral and in Pledgor’s possession to Bank immediately, or if hereafter acquired, immediately following acquisition, in a form suitable for transfer by delivery or accompanied by duly executed instruments of transfer or assignment in blank with signatures appropriately guaranteed in form and substance suitable to Bank.

8. Change of Name/Status. Pledgor shall not change its name, change its corporate status, use any trade name or engage in any business not reasonably related to its business as presently conducted.

9. Power of Attorney. Pledgor appoints Bank and any officer thereof as Pledgor’s attorney-in-fact with full power in Pledgor’s name and on Pledgor’s behalf to do every act which Pledgor is obligated to do or may be required to do hereunder; however, nothing in this paragraph shall be construed to obligate Bank to take any action hereunder nor shall Bank be liable to Pledgor for failure to take any action hereunder. This appointment shall be deemed a power coupled with an interest and shall not be terminable as long as the Obligations are outstanding and shall not terminate on the disability or incompetence of Pledgor. Without limiting the generality of the foregoing, Bank shall have the right and power to receive, indorse and collect all checks and other orders for the payment of money made payable to Pledgor representing any dividend, interest payment or other distribution payable in respect of the Collateral or any part thereof.

10. Other Parties and Other Collateral. No renewal or extensions of or any other indulgence with respect to the Obligations or any part thereof, no modification of the document(s) evidencing the Obligations, no release of any security, no release of any person (including any maker, indorser, guarantor or surety) liable on the

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Obligations, no delay in enforcement of payment, and no delay or omission or lack of diligence or care in exercising any right or power with respect to the Obligations or any security therefor or guaranty thereof or under this Agreement shall in any manner impair or affect the rights of Bank under any law, hereunder, or under any other agreement pertaining to the Collateral. Bank need not file suit or assert a claim for personal judgment against any person for any part of the Obligations or seek to realize upon any other security for the Obligations, before foreclosing or otherwise realizing upon the Collateral. Pledgor waives any right that can be waived to the benefit of or to require or control application of any other security or proceeds thereof, and agrees that Bank shall have no duty or obligation to Pledgor to apply to the Obligations any such other security or proceeds thereof

11. Waivers by Pledgor. Pledgor waives notice of the creation, advance, increase, existence, extension or renewal of, and of any indulgence with respect to, the Obligations; waives presentment, demand, notice of dishonor, and protest; waives notice of the amount of the Obligations outstanding at any time, notice of any change in financial condition of any person liable for the Obligations or any part thereof, notice of any Event of Default, and all other notices respecting the Obligations; and agrees that maturity of the Obligations and any part thereof may be accelerated, extended or renewed one or more times by Bank in its discretion, without notice to Pledgor. Pledgor waives any right to require that any action be brought against any other person or to require that resort be had to any other security or to any balance of any deposit account. Pledgor further waives any right of subrogation or to enforce any right of action against any other pledgor until the Obligations are paid in full.

12. Reserved.

F. Rights and Powers of Bank.

1. General. Bank, before or after default, without liability to Pledgor may: take control of proceeds, including stock received as dividends or by reason of stock splits; release the Collateral in its possession to any Pledgor, temporarily or otherwise; reject as unsatisfactory any property hereafter offered by Pledgor as Collateral; take control of funds generated by the Collateral (except as otherwise provided in Section D above, such as cash dividends, interest and proceeds, and use same to reduce any part of the Obligations and exercise all other rights which an owner of such Collateral may exercise, except the right to vote or dispose of the Collateral before an Event of Default; and at any time after an Event of Default transfer any of the Collateral or evidence thereof into its own name or that of its nominee. Bank shall not be liable for failure to collect any account or instruments, or for any act or omission on the part of Bank, its officers, agents or employees, except for its or their own willful misconduct or gross negligence. The foregoing rights and powers of Bank will be in addition to, and not a limitation upon, any rights and powers of Bank given by law, elsewhere in this Agreement, or otherwise.

2. Convertible Collateral. Bank may present for conversion any Collateral which is convertible into any other instrument or investment security or a combination thereof with cash, but Bank shall not have any duty to present for conversion any Collateral unless it shall have received from Pledgor detailed written instructions to that effect at a time reasonably far in advance of the final conversion date to make such conversion possible.

G. Default.

1. Event of Default. An event of default (“Event of Default”) shall occur and be continuing (a) if Pledgor or any other obligor on all or part of the Obligations shall fail to timely and properly pay or observe, keep or perform any term, covenant, agreement or condition in this Agreement, and such failure continues for five (5) days after written notice from Lender to Borrower, or in any other agreement between Pledgor and Bank or between Bank and any other obligor on the Obligations, including but not limited to any other note or instrument, loan agreement, security agreement, promissory note, or other agreement or instrument concerning the Obligations, (in all events, subject to grace periods and requisites of notice and ability to cure set forth therein); or (b) an Event of Default (as defined in the Loan Agreement) shall occur and be continuing.

2. Rights and Remedies. If any Event of Default shall occur, then, in each and every such case, Bank may, without (a) presentment, demand, or protest, (b) notice of default, dishonor, demand, non-payment, or protest, (c) notice of intent to accelerate all or any part of the Obligations, (d) notice of acceleration of all or any part of the Obligations, or (e) notice of any other kind, all of which Pledgor hereby expressly waives (except for any

PLEDGE AGREEMENT – Brooks - $2,000,000 – Page 4

notice required under this Agreement, any other loan document or which may not be waived under applicable law), at any time thereafter exercise and/or enforce any of the following rights and remedies, at Bank’s option:

A. Acceleration. The Obligations shall, at Bank’s option, become immediately due and payable, and the obligation, if any, of Bank to permit further borrowings under the Obligations shall at Bank’s option immediately cease and terminate.

B. Liquidation of Collateral. Sell, or instruct any Agent or Broker to sell, all or any part of the Collateral in a public or private sale, direct any Agent or Broker to liquidate all or any part of any Account and deliver all proceeds thereof to Bank, and apply all proceeds to the payment of any or all of the Obligations in such order and manner as Bank shall, in its discretion, choose, or exercise any remedy provided for in Section F or G hereof, in the Loan Agreement or in the Note.

C. Uniform Commercial Code. All of the rights, powers and remedies of a secured creditor under the Uniform Commercial Code (“UCC’) as adopted in the jurisdiction to which Bank is subject under this Agreement.

D. Right of Set Off. Without notice or demand to Pledgor, set off and apply against any and all of the Obligations any and all deposits (general or special, time or demand, provisional or final) and any other indebtedness, at any time held or owing by Bank or by any of Bank’s affiliates or correspondents to or for the credit of the account of Pledgor or any guarantor or indorser of Pledgor’s Obligations.

Pledgor specifically understands and agrees that any sale by Bank of all or part of the Collateral pursuant to the terms of this Agreement may be effected by Bank at times and in manners which could result in the proceeds of such sale as being significantly and materially less than might have been received if such sale had occurred at different times or in different manners, and Pledgor hereby releases Bank and its officers and representatives from and against any and all obligations and liabilities arising out of or related to the timing or manner of any such sale.

If, in the opinion of Bank, there is any question that a public sale or distribution of any Collateral will violate any state or federal securities law, Bank may offer and sell such Collateral in a transaction exempt from registration under federal securities law, and any such sale made in good faith by Bank shall be deemed ‘‘commercially reasonable.’’

H. General

1. Parties Bound. Bank’s rights hereunder shall inure to the benefit of its successors and assigns, and in the event of any assignment or transfer of any of the Obligations or the Collateral, Bank thereafter shall be fully discharged from any responsibility with respect to the Collateral so assigned or transferred, but Bank shall retain all rights and powers hereby given with respect to any of the Obligations or the Collateral not so assigned or transferred. All representations, warranties and agreements of Pledgor if more than one are joint and several and all shall be binding upon the personal representatives, heirs, successors and assigns of Pledgor.

2. Waiver. No delay of Bank in exercising any power or right shall operate as a waiver thereof; nor shall any single or partial exercise of any power or right preclude other or further exercise thereof or the exercise of any other power or right. No waiver by Bank of any right hereunder or of any default by Pledgor shall be binding upon Bank unless in writing, and no failure by Bank to exercise any power or right hereunder or waiver of any default by Pledgor shall operate as a waiver of any other or further exercise of such right or power or of any further default. Each right, power and remedy of Bank as provided for herein or in any of the loan documents related to the Obligations, or which shall now or hereafter exist at law or in equity or by statute or otherwise, shall be cumulative and concurrent and shall be in addition to every other such right, power or remedy. The exercise or beginning of the exercise by Bank of any one or more of such rights, powers or remedies shall not preclude the simultaneous or later exercise by Bank of any or all other such rights, powers or remedies.

PLEDGE AGREEMENT – Brooks - $2,000,000 – Page 5

3. Agreement Continuing. This Agreement shall constitute a continuing agreement. This Agreement shall apply to all future as well as existing transactions, whether or not of the character contemplated at the date of this Agreement, and if all transactions between Bank and Pledgor shall be closed at any time, shall be equally applicable to any new transactions thereafter. Provisions of this Agreement, unless by their terms exclusive, shall be in addition to other agreements between the parties. Time is of the essence of this Agreement. Notwithstanding the foregoing, in the event that all Obligations are fully and finally paid and all commitments of the Bank to extend credit to Borrower have been terminated, then this Agreement shall be terminated, and all Collateral shall, at the request of the Pledgor be released.

4. Definitions. Unless the context indicates otherwise, definitions in the UCC apply to words and phrases in this Agreement; if UCC definitions conflict, Article 8 and/or 9 definitions apply.

5. Notice. Notice shall be deemed reasonable if mailed postage prepaid at least 5 days before the related action (or if the UCC elsewhere specifies a longer period, such longer period) to the address of Pledgor given above. Each notice, request and demand shall be deemed given or made, if sent by mail, upon the earlier of the date of receipt or five (5) days after deposit in the U.S. Mail, first class postage prepaid, or if sent by any other means, upon delivery.

6. Modifications. No provision hereof shall be modified or limited except by a written agreement expressly referring hereto and to the provisions so modified or limited and signed by Pledgor and Bank. The provisions of this Agreement shall not be modified or limited by course of conduct or usage of trade.

7. Partial Invalidity. The unenforceability or invalidity of any provision of this Agreement shall not affect the enforceability or validity of any other provision herein, and the invalidity or unenforceability of any provision of any loan document related to the Obligations to any person or circumstance shall not affect the enforceability or validity of such provision as it may apply to other persons or circumstances.

8. Applicable Law and Venue. This Agreement has been delivered in the State of Texas and shall be construed in accordance with the laws of that State. It is performable by Pledgor in the county or city of Bank’s address set out above and Pledgor expressly waives any objection as to venue in any such location. Wherever possible each provision of this Agreement shall be interpreted in such manner as to be effective and valid under applicable law, but if any provision of this Agreement shall be prohibited by or invalid under applicable law, such provision shall be ineffective to the extent of such prohibition or invalidity, without invalidating the remainder of such provisions or the remaining provisions of this Agreement.

9. Financing Statement. To the extent permitted by applicable law, a carbon, photographic or other reproduction of this Agreement or any financing statement covering the Collateral shall be sufficient as a financing statement, and Bank is authorized to file this Agreement or any other financing statements it determines to be necessary or prudent.

THIS WRITTEN AGREEMENT AND ANY OTHER DOCUMENTS EXECUTED IN CONNECTION HEREWITH REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly executed by their duly authorized representatives as of the date first above written.

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Exhibit 4

TIB - THE INDEPENDENT BANKERSBANK

PROMISSORY NOTE

FOR VALUE RECEIVED, the undersigned, DAVID BROOKS (“Maker”), promises to pay to the order of TIB—THE INDEPENDENT BANKERSBANK (“Payee”) the Principal sum of Three Hundred Thousand and No/100 Dollars ($300,000.00), or so much thereof as shall be advanced hereunder, on demand, at or before the maturity of this Note, with interest on the unpaid balance outstanding from time to time at the rate or rates specified below, both principal and interest payable as provided below in lawful money of the United States of America at the address of Payee set forth below or at such other place as from time to time may be designated by the holder of this Note.

I. Interest Rates and Payments

Prior to default or maturity, the unpaid principal of this Note from time to time outstanding shall bear interest at the rate (“Rate”) of interest per annum equal to the greater of (i) four and one-half percent (4.50%) (the “Floor”) or (ii) the rate reported in the Credit Markets section (or similar section) of The Wall Street Journal as the U.S. “Prime Rate”, as announced from time to time automatically fluctuating upward and downward with each announcement without notice to Maker or any other person (the “Index”), provided that in no event shall the Rate exceed the maximum interest rate permitted under applicable law (“Maximum Rate”). If hereafter the Index shall change, the rate of interest on the unpaid balance of principal of this Note prior to maturity shall be increased or decreased, as the case may be, from time to time as of the effective date of each change in the Index (but in no event less than the Floor). If applicable law provides for a ceiling, that ceiling shall be the indicated rate ceiling. All interest accruing under this Note shall be calculated on the basis of a 360-day year applied to the actual number of days elapsed.

Payments of principal in the amount of $37,500.00 (which is an amount necessary to amortize the stated principal hereof over a 48-month period [“Amortization Period”]), plus accrued and unpaid interest, shall be due and payable commencing on June 30, 2011 and continuing on each December 31 and June 30 thereafter until and including December 31, 2014, on which date all accrued and unpaid interest, principal (which may be a balloon payment), and other charges under this Note shall be fully due and payable. Any payment received later than ten (10) days from the due date thereof must be accompanied by a late fee payment in the amount of five percent (5%) of the amount of such monthly payment.

All principal and interest which is matured or otherwise past due under this Note shall bear interest at the Maximum Rate, or, if no such rate is designated under applicable law, at the rate of eighteen percent (18%) per annum.

Maker shall have the right to prepay, without penalty, at any time and from time to time prior to maturity, all or any part of the unpaid principal balance of this Note and all or any part of the unpaid interest accrued to the date of such prepayment, provided that any such principal thus paid is accompanied by accrued interest on such principal. Any partial prepayments of principal shall be applied to installments thereof in the inverse order of maturity.

II. Security

This Note is secured by, inter alia, a Pledge Agreement (the “Pledge Agreement”) of even date herewith from Maker to Payee, to which Pledge Agreement reference is made for a description of the property covered thereby and the nature and extent of the rights and powers of the holder of this Note in respect of such property.

III. Right to Accelerate Upon Default

The holder of this Note shall have the option of declaring the principal balance hereof and the interest accrued hereon to be immediately due and payable upon the failure of Maker to pay any installment of the principal of or interest on this Note when due and such failure shall continue for a period of five (5) days after notice from Payee to Maker, or upon the occurrence of a default specified in the Pledge Agreement or in any other document securing or evidencing the obligations established by this Note (this Note, the Pledge Agreement, and any such other documents are called the “Loan Documents” below), and the continuance of such default for a relevant grace or notice period provided therein.

IV. Waiver of Conditions and Defenses to Liability

Maker and any other party who is or becomes liable to pay all or any part of this Note, or who grants any lien or security interest to secure all or any part of this Note (each called an “other liable party” below), including but not limited to any drawer, acceptor, endorser, guarantor, surety or accommodation party, severally waive presentment for payment, demand, notice of demand and of dishonor and nonpayment of this Note, notice of intention to accelerate the maturity of this Note, protest and notice of protest, diligence in collecting, and the bringing of suit against any other party.

Further, Maker and any other liable party severally waive any notice of or defense based upon any agreement or consent of the holder of this Note made or given from time to time, before or after maturity, to any of the following: the acceleration, renewal or extension of this Note; a change in the time or manner of payments required by this Note; a change in the rates of interest specified in this Note; acceptance or surrender of security; a substitution of security or subordination, amendment or release of security; an addition or release of any other liable party; changes of any sort whatever in the terms of payment of this Note or in the manner of doing business with Maker; and any settlement or compromise with Maker or any other liable party on such terms as the holder of this Note may deem appropriate in its sole and absolute discretion.

The holder of this Note may apply all moneys received from Maker or others, or from any security (whether held under a security instrument or not), in such manner upon the indebtedness evidenced or secured by any Loan Documents (whether then due or not) as such holder may determine to be in its best interest, without in any way being required to marshal assets or to apply all or any part of such moneys upon any particular part of such indebtedness. The holder of this Note is not required to retain, hold, protect, exercise due care with respect to, perfect security interests in or otherwise assure or safeguard any security for this Note, and no failure by the holder of this Note to do any of the foregoing and no exercise or failure to exercise by such holder of any other right or remedy shall in any way affect any of Maker’s or any other liable party’s obligations hereunder or under other Loan Documents or affect any security or give Maker or any other liable party any recourse against the holder of this Note.

V. Usury Savings Provision

It is the intent of Maker and Payee in the execution of this Note and all other Loan Documents to contract in strict compliance with applicable usury law. In furtherance thereof, Maker and Payee stipulate and agree that none of the terms and provisions contained in this Note, or in any other instrument executed in connection herewith, shall ever be construed to create a contract to pay for the use, forbearance or detention of money, interest at a rate in excess of the Maximum Rate. Neither Maker nor any guarantors, endorsers or other parties now or hereafter becoming liable for payment of this Note shall ever be obligated or required to pay interest on this Note at a rate in excess of the Maximum Rate, and the provisions of this paragraph shall control over all other provisions of this Note and any other Loan Documents now or hereafter executed which may be in apparent conflict herewith. Payee expressly disavows any intention to charge or collect excessive unearned interest or finance charges in the event the maturity of this Note is accelerated. If the maturity of this Note shall be accelerated for any reason or if the principal of this Note is paid prior to the end of the term of this Note, and as a result thereof the interest received for the actual period of existence of the loan evidenced by this Note exceeds the applicable maximum lawful rate, the holder of this Note shall credit the amount of such excess against the principal balance of this Note then outstanding and thereby shall render inapplicable any and all penalties of any kind provided by applicable law as a result of such excess interest; provided, however, that if the principal hereof has been paid in full, such excess shall be refunded to Maker. If the holder of this Note shall receive money (or anything else) which is determined to constitute interest and which would increase the effective interest rate on this Note or the other indebtedness secured by the Loan Documents to a rate in excess of that permitted by applicable law, the amount determined to constitute interest in excess of the lawful rate shall be credited against the principal balance of this Note then outstanding or, if the principal balance has been paid in full, refunded to Maker, in which event any and all penalties of any kind under applicable law as a result of such excess interest shall be inapplicable. If the holder of this Note shall not actually receive, but shall contract for, request or demand, a payment of money (or anything else) which is determined to constitute interest and which would increase the effective interest rate contracted for or charged on this Note or the other indebtedness evidenced or secured by the Loan Documents to a rate in excess of that permitted by applicable law, the holder of this Note shall be entitled, following such determination, to waive or rescind the contractual claim, request or demand for the amount determined to constitute interest in excess of the lawful rate, in which event any and all penalties of any kind under applicable law as a result of such excess interest shall be inapplicable. By execution of this Note Maker acknowledges that Maker believes the loan evidenced by this Note to be non-usurious and agrees that if, at any time, Maker should have reason to believe that such loan is in fact usurious, Maker will give the holder of this Note notice of such condition and Maker agrees that the holder shall have sixty (60) days in which to make appropriate refund or other adjustment in order to correct such condition if in fact such exists. Additionally, if, from any circumstance whatsoever, fulfillment of any provision hereof or any other Loan Documents shall, at the time fulfillment of such provision be due, involve transcending the Maximum Rate then, ipso facto, the obligation to be fulfilled shall be reduced to the Maximum Rate. The term “applicable law” as used in this Note shall mean the laws of the State of Texas or the laws of the United States, whichever laws allow the greater rate of interest, as such laws now exist or may be changed or amended or come into effect in the future.

VI. Miscellaneous

Should the indebtedness represented by this Note or any part thereof be collected at law or in equity or through any bankruptcy, receivership, probate or other court proceedings or if this Note is placed in the hands of attorneys for collection after default, Maker and all endorsers, guarantors and sureties of this Note jointly and severally agree to pay to the holder of this Note in addition to the principal and interest due and payable hereon all the costs and expenses of the holder in enforcing this Note including, without limitation, reasonable attorneys’ fees and legal expenses.

This Note and the rights, duties and liabilities of the parties hereunder or arising from or relating in any way to the indebtedness evidenced by this Note or the transaction of which such indebtedness is a part shall be governed by and construed in accordance with the law of the State of Texas and the law of the United States applicable to transactions within such State.

No amendment of this Note shall be binding unless expressed in a writing executed by Maker and the holder of this Note.

Maker certifies, represents, and warrants to Payee that the proceeds hereof are to be used for a commercial purpose and not for personal, family, household, or agricultural purposes.

THE PARTIES HERETO VOLUNTARILY AND KNOWINGLY WAIVE ANY AND ALL RIGHTS TO A TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM BROUGHT BY EITHER PARTY ON ANY MATTER WHATSOEVER ARISING OUT OF, IN CONNECTION WITH, OR RELATED TO ANY OF THE LOAN DOCUMENTS.

MAKER IRREVOCABLY SUBMITS TO THE NON-EXCLUSIVE JURISDICTION OF ANY TEXAS OR FEDERAL COURT SITTING IN DALLAS COUNTY, TEXAS OVER ANY SUIT, ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO ANY OF THE LOAN DOCUMENTS, AND MAKER HEREBY AGREES AND CONSENTS THAT, IN ADDITION TO ANY METHODS OF SERVICE OF PROCESS PROVIDED FOR UNDER APPLICABLE LAW, ALL SERVICE OF PROCESS IN ANY SUCH SUIT, ACTION OR PROCEEDING IN ANY TEXAS OR FEDERAL COURT SITTING IN DALLAS COUNTY, TEXAS (OR SUCH OTHER COUNTY IN TEXAS) MAY BE MADE BY CERTIFIED OR REGISTERED MAIL, RETURN RECEIPT REQUESTED, DIRECTED TO MAKER AT THE ADDRESS INDICATED BELOW, AND SERVICE SO MADE SHALL BE COMPLETE FIVE DAYS AFTER THE SAME SHALL HAVE BEEN SO MAILED.

Payee’s Address:

TIB-THE INDEPENDENT BANKERSBANK

P.O. Box 560528

Dallas, TX 75356-0528

Exhibit 5

A. Security Interest. For good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, Pledgor/Debtor (hereinafter referred to as “Pledgor,” whether one or more) pledges, assigns and

grants to Bank a security interest and lien in the Collateral (hereinafter defined) to secure the payment and the performance of the Obligations (hereinafter defined).

B. Collateral. The security interest is granted in the following collateral (the “Collateral”):

1. 295,550 shares of the outstanding Common Stock of Independent Bank Group, Inc. (“IBG”).

2. Reserved.

3. All additions, substitutes and replacements for and proceeds of the above Collateral (including all income and benefits resulting from any of the above, such as dividends payable or distributable in cash, property or stock; interest, premium and principal payments; redemption proceeds and subscription rights; and shares or other proceeds of conversions or splits of any securities in the Collateral).

4. The balance of every deposit account of Pledgor maintained with Bank and any other claim of Pledgor against Bank, now or hereafter existing, liquidated or unliquidated, and all money, instruments, investment property, securities, documents, chattel paper, credits, claims, demands, income, and any other property, rights and interests of Pledgor which at any time shall come into the possession or custody or under the control of Bank or any of its agents or affiliates, for any purpose, and the proceeds of any thereof. Bank shall be deemed to have possession of any of the Collateral in transit to or set apart for it or any of its agents or affiliates.

C. Obligations.

1. Description of Obligations. The following obligations (“Obligations”) are secured by this Agreement: (a) all debts, obligations, liabilities and agreements of DAVID BROOKS (“Borrower”), to Bank, now or hereafter existing, arising directly or indirectly between Borrower and Bank whether absolute or contingent, joint or several, secured or unsecured, due or not due, contractual or tortious, liquidated or unliquidated, arising by operation of law or otherwise, and all renewals, extensions or rearrangement of any of the above; (b) all costs incurred by Bank to obtain, preserve, perfect and enforce this Agreement and maintain, preserve, collect and enforce the Collateral; (c) all debts, obligations, liabilities and agreements of Pledgor to Bank under this Agreement; (d) interest on the above amounts determined in accordance with applicable agreements between Bank and Pledgor or between Bank and Borrower; (e) all indebtedness, liabilities and obligations of Borrower to Bank under the Loan Agreement dated even date hereof (the “Loan Agreement”) between Borrower and Bank and all renewals, extensions and modifications thereof; (f) all indebtedness, liabilities and obligations of Borrower to Bank under the Promissory Note dated the date hereof (the “Note”) in the stated principal amount of $300,000 payable by

Borrower to the order of Bank and all renewals, extensions and modifications thereof; (g) all indebtedness, liabilities and obligations of Borrower to Bank under that certain Promissory Note dated on or about December 15, 2008 (as subsequently, renewed, modified, and amended, “Loan #86918”) in the original stated principal amount of $2,000,000.00 payable by Borrower to the order of Bank and all renewals, extensions and modifications thereof; and (h) all reasonable expenses of the Bank, including reasonable fees and expenses of the Bank’s counsel, incident to the enforcement of payment of all obligations of the Pledgor by any action or participation in, or in connection with a case or proceeding under the Bankruptcy Code, or any successor statute thereto.

In the event any amount paid to Bank on any of the Obligations is subsequently recovered from Bank in or as a result of any bankruptcy, insolvency or fraudulent conveyance proceeding involving an obligor of the Obligations other than Pledgor, Pledgor shall be liable to Bank for the amounts so recovered up to the fair market value of the Collateral whether or not the Collateral has been released or the security interest terminated. In the event the Collateral has been released or the security interest terminated, the fair market value of the Collateral shall be determined, at Bank’s option, as of the date the Collateral was released, the security interest terminated, or said amounts were recovered.

2. Use of Proceeds. The proceeds of any indebtedness or obligation secured by the Collateral will not be used directly or indirectly to purchase or carry any “margin stock” as that term is defined in Regulation U of the Board of Governors of the Federal Reserve System, or extend credit to or invest in other parties for the purpose of purchasing or carrying any such “margin stock,” or to reduce or retire any indebtedness incurred for such purpose or otherwise in a manner which would violate Regulations T or U.

D. Pledgor’s Warranties. Pledgor hereby represents and warrants to Bank as follows:

1. Financing Statements. Except as may be noted by schedule attached hereto and incorporated herein by reference, no financing statement covering the Collateral is or will be on file in any public office, except the financing statements relating to this security interest, and no security interest, other than the one herein created, has attached or been perfected in the Collateral or any part thereof.

2. Ownership. Pledgor owns, or will use the proceeds of any loans by Bank to become the owner of, the Collateral free from any setoff, claim, restriction, lien, security interest or encumbrance except liens for taxes not yet due and payable and the security interest hereunder.

3. Power and Authority. Pledgor has full power and authority to make this Agreement, and all necessary consents and approvals of any persons, entities, governmental or regulatory authorities and securities exchanges have been obtained to effectuate the validity of this Agreement.

E. Pledgor’s Covenants. Until full payment and performance of all of the Obligations and termination or expiration of any obligation or commitment of Bank to make advances or loans to Borrower, unless Bank otherwise consents in writing:

1. Obligations and This Agreement. Pledgor shall perform all of its agreements herein and in any other agreements between it and Bank.

2. Ownership of and Rights in Collateral. Pledgor shall defend the Collateral against all claims and demands of all persons at any time claiming any interest therein adverse to Bank. Pledgor shall keep the Collateral free from all liens and security interests except those for taxes not yet due and payable and the security interest hereby created. Any investment property and/or securities received by Pledgor, which shall comprise additions, substitutes and replacements for, or proceeds of, the Collateral, shall be held in trust for Bank and shall be delivered immediately to Bank. Any cash proceeds from the Collateral shall be held in trust for Bank and upon demand shall be delivered immediately to Bank.

3. Bank’s Costs. Pledgor shall pay all costs necessary to obtain, preserve, perfect, defend and enforce the security interest created by this Agreement, collect the Obligations, and preserve, defend, enforce and collect the Collateral, including but not limited to taxes, assessments, reasonable attorneys’ fees, legal expenses and expenses of sales. Whether the Collateral is or is not in Bank’s possession, and without any obligation to do so and without waiving Pledgor’s default for failure to make any such payment, Bank at its option may pay any such costs and expenses and discharge encumbrances on the Collateral, and such payments shall be a part of the Obligations and bear interest at the rate set out in the Obligations. Pledgor agrees to reimburse Bank on demand for any costs so incurred.

4. Information and Inspection. Pledgor shall (i) promptly furnish Bank any information with respect to the Collateral reasonably requested by Bank; (ii) allow Bank or its representatives to inspect and copy, or furnish Bank or its representatives with copies of, all records relating to the Collateral and the Obligations; and (iii) promptly furnish Bank or its representatives with any other information Bank may reasonably request.

5. Additional Documents. Pledgor shall sign and deliver any papers furnished by Bank which are necessary or desirable in the judgment of Bank to obtain, maintain and perfect the security interest hereunder and to enable Bank to comply with any federal or state law in order to obtain or perfect Bank’s interest in the Collateral or to obtain proceeds of the Collateral.

6. Notice of Changes. Pledgor shall notify Bank immediately of (i) any material change in the Collateral, (ii) a change in Pledgor’s residence or location, (iii) a change in any matter warranted or represented by Pledgor in this Agreement, or in any of the loan documents relating to the Obligations or furnished to Bank pursuant to this Agreement, and (iv) the occurrence of an Event of Default as defined herein.

7. Possession of Collateral. Pledgor shall deliver a copy of this Agreement (or other notice acceptable to Bank) to any Broker, financial intermediary, or any other person in possession of any of the Collateral or on whose books the interest of Pledgor in the Collateral appears, and such delivery shall constitute notice to such person of Bank’s security interest in the Collateral and shall constitute Pledgor’s instruction to such person to note Bank’s security interest on their books and records, or deliver to Bank certificates or other evidence of the Collateral promptly upon Bank’s request. Pledgor shall deliver all investment securities and other instruments and documents which are a part of the Collateral and in Pledgor’s possession to Bank immediately, or if hereafter acquired, immediately following acquisition, in a form suitable for transfer by delivery or accompanied by duly executed instruments of transfer or assignment in blank with signatures appropriately guaranteed in form and substance suitable to Bank.

8. Change of Name/Status. Pledgor shall not change its name, change its corporate status, use any trade name or engage in any business not reasonably related to its business as presently conducted.

9. Power of Attorney. Pledgor appoints Bank and any officer thereof as Pledgor’s attorney-in-fact with full power in Pledgor’s name and on Pledgor’s behalf to do every act which Pledgor is obligated to do or may be required to do hereunder; however, nothing in this paragraph shall be construed to obligate Bank to take any action hereunder nor shall Bank be liable to Pledgor for failure to take any action hereunder. This appointment shall be deemed a power coupled with an interest and shall not be terminable as long as the Obligations are outstanding and shall not terminate on the disability or incompetence of Pledgor. Without limiting the generality of the foregoing, Bank shall have the right and power to receive, indorse and collect all checks and other orders for the payment of money made payable to Pledgor representing any dividend, interest payment or other distribution payable in respect of the Collateral or any part thereof.

10. Other Parties and Other Collateral. No renewal or extensions of or any other indulgence with respect to the Obligations or any part thereof, no modification of the document(s) evidencing the Obligations, no release of any security, no release of any person (including any maker, indorser, guarantor or surety) liable on the Obligations, no delay in enforcement of payment, and no delay or omission or lack of diligence or care in exercising any right or power with respect to the Obligations or any security therefor or guaranty thereof or under this Agreement shall in any manner impair or affect the rights of Bank under any law, hereunder, or under any other agreement pertaining to the Collateral. Bank need not file suit or assert a claim for personal judgment against any person for any part of the Obligations or seek to realize upon any other security for the Obligations, before foreclosing or otherwise realizing upon the Collateral. Pledgor waives any right that can be waived to the benefit of or to require or control application of any other security or proceeds thereof, and agrees that Bank shall have no duty or obligation to Pledgor to apply to the Obligations any such other security or proceeds thereof.

11. Waivers by Pledgor. Pledgor waives notice of the creation, advance, increase, existence, extension or renewal of, and of any indulgence with respect to, the Obligations; waives presentment, demand, notice of dishonor, and protest; waives notice of the amount of the Obligations outstanding at any time, notice of any change in financial condition of any person liable for the Obligations or any part thereof, notice of any Event of Default, and all other notices respecting the Obligations; and agrees that maturity of the Obligations and any part thereof may be accelerated, extended or renewed one or more times by Bank in its discretion, without notice to Pledgor. Pledgor waives any right to require that any action be brought against any other person or to require that resort be had to any other security or to any balance of any deposit account. Pledgor further waives any right of subrogation or to enforce any right of action against any other pledgor until the Obligations are paid in full.

12. Reserved.

F. Rights and Powers of Bank.

1. General. Bank, before or after default, without liability to Pledgor may: take control of proceeds, including stock received as dividends or by reason of stock splits; release the Collateral in its possession to any Pledgor, temporarily or otherwise; reject as unsatisfactory any property hereafter offered by Pledgor as Collateral; take control of funds generated by the Collateral (except as otherwise provided in Section D above, such as cash dividends, interest and proceeds, and use same to reduce any part of the Obligations and exercise all other rights which an owner of such Collateral may exercise, except the right to vote or dispose of the Collateral before an Event of Default; and at any time after an Event of Default transfer any of the Collateral or evidence thereof into its own name or that of its nominee. Bank shall not be liable for failure to collect any account or instruments, or for any act or omission on the part of Bank, its officers, agents or employees, except for its or their own willful misconduct or gross negligence. The foregoing rights and powers of Bank will be in addition to, and not a limitation upon, any rights and powers of Bank given by law, elsewhere in this Agreement, or otherwise.

2. Convertible Collateral. Bank may present for conversion any Collateral which is convertible into any other instrument or investment security or a combination thereof with cash, but Bank shall not have any duty to present for conversion any Collateral unless it shall have received from Pledgor detailed written instructions to that effect at a time reasonably far in advance of the final conversion date to make such conversion possible.

G. Default.

1. Event of Default. An event of default (“Event of Default”) shall occur and be continuing (a) if Pledgor or any other obligor on all or part of the Obligations shall fail to timely and properly pay or observe, keep or perform any term, covenant, agreement or condition in this Agreement, and such failure continues for five (5) days after written notice from Lender to Borrower, or in any other agreement between Pledgor and Bank or between Bank and any other obligor on the Obligations, including but not limited to any other note or instrument, loan agreement, security agreement, promissory note, or other agreement or instrument concerning the Obligations, (in all events, subject to grace periods and requisites of notice and ability to cure set forth therein); or (b) an Event of Default (as defined in the Loan Agreement) shall occur and be continuing.

2. Rights and Remedies. If any Event of Default shall occur, then, in each and every such case, Bank may, without (a) presentment, demand, or protest, (b) notice of default, dishonor, demand, non-payment, or protest, (c) notice of intent to accelerate all or any part of the Obligations, (d) notice of acceleration of all or any part of the Obligations, or (e) notice of any other kind, all of which Pledgor hereby expressly waives (except for any notice required under this Agreement, any other loan document or which may not be waived under applicable law), at any time thereafter exercise and/or enforce any of the following rights and remedies, at Bank’s option:

A. Acceleration. The Obligations shall, at Bank’s option, become immediately due and payable, and the obligation, if any, of Bank to permit further borrowings under the Obligations shall at Bank’s option immediately cease and terminate.

B. Liquidation of Collateral. Sell, or instruct any Agent or Broker to sell, all or any part of the Collateral in a public or private sale, direct any Agent or Broker to liquidate all or any part of any Account and deliver all proceeds thereof to Bank, and apply all proceeds to the payment of any or all of the Obligations in such order and manner as Bank shall, in its discretion, choose, or exercise any remedy provided for in Section F or G, in the Loan Agreement or in the Note.

C. Uniform Commercial Code. All of the rights, powers and remedies of a secured creditor under the Uniform Commercial Code (“UCC’) as adopted in the jurisdiction to which Bank is subject under this Agreement.

D. Right of Set Off. Without notice or demand to Pledgor, set off and apply against any and all of the Obligations any and all deposits (general or special, time or demand, provisional or final) and any other indebtedness, at any time held or owing by Bank or by any of Bank’s affiliates or correspondents to or for the credit of the account of Pledgor or any guarantor or indorser of Pledgor’s Obligations.

Pledgor specifically understands and agrees that any sale by Bank of all or part of the Collateral pursuant to the terms of this Agreement may be effected by Bank at times and in manners which could result in the proceeds of such sale as being significantly and materially less than might have been received if such sale had occurred at different times or in different manners, and Pledgor hereby releases Bank and its officers and representatives from and against any and all obligations and liabilities arising out of or related to the timing or manner of any such sale.

If, in the opinion of Bank, there is any question that a public sale or distribution of any Collateral will violate any state or federal securities law, Bank may offer and sell such Collateral in a transaction exempt from registration under federal securities law, and any such sale made in good faith by Bank shall be deemed “commercially reasonable.”

H. General

1. Parties Bound. Bank’s rights hereunder shall inure to the benefit of its successors and assigns, and in the event of any assignment or transfer of any of the Obligations or the Collateral, Bank thereafter shall be fully discharged from any responsibility with respect to the Collateral so assigned or transferred, but Bank shall retain all rights and powers hereby given with respect to any of the Obligations or the Collateral not so assigned or transferred. All representations, warranties and agreements of Pledgor if more than one are joint and several and all shall be binding upon the personal representatives, heirs, successors and assigns of Pledgor.

2. Waiver. No delay of Bank in exercising any power or right shall operate as a waiver thereof; nor shall any single or partial exercise of any power or right preclude other or further exercise thereof or the exercise of any other power or right. No waiver by Bank of any right hereunder or of any default by Pledgor shall be binding upon Bank unless in writing, and no failure by Bank to exercise any power or right hereunder or waiver of any default by Pledgor shall operate as a waiver of any other or further exercise of such right or power or of any further default. Each right, power and remedy of Bank as provided for herein or in any of the loan documents related to the Obligations, or which shall now or hereafter exist at law or in equity or by statute or otherwise, shall be cumulative and concurrent and shall be in addition to every other such right, power or remedy. The exercise or beginning of the exercise by Bank of any one or more of such rights, powers or remedies shall not preclude the simultaneous or later exercise by Bank of any or all other such rights, powers or remedies.

3. Agreement Continuing. This Agreement shall constitute a continuing agreement. This Agreement shall apply to all future as well as existing transactions, whether or not of the character contemplated at the date of this Agreement, and if all transactions between Bank and Pledgor shall be closed at any time, shall be equally applicable to any new transactions thereafter. Provisions of this Agreement, unless by their terms exclusive, shall be in addition to other agreements between the parties. Time is of the essence of this Agreement. Notwithstanding the foregoing, in the event that all Obligations are fully and finally paid and all commitments of the Bank to extend credit to Borrower have been terminated, then this Agreement shall be terminated, and all Collateral shall, at the request of the Pledgor be released.

4. Definitions. Unless the context indicates otherwise, definitions in the UCC apply to words and phrases in this Agreement; if UCC definitions conflict, Article 8 and/or 9 definitions apply.

5. Notice. Notice shall be deemed reasonable if mailed postage prepaid at least 5 days before the related action (or if the UCC elsewhere specifies a longer period, such longer period) to the address of Pledgor given Above. Each notice, request and demand shall be deemed given or made, if sent by mail, upon the earlier of the date of receipt or five (5) days after deposit in the U.S. Mail, first class postage prepaid, or if sent by any other means, upon delivery.

6. Modifications. No provision hereof shall be modified or limited except by a written agreement expressly referring hereto and to the provisions so modified or limited and signed by Pledgor and Bank. The provisions of this Agreement shall not be modified or limited by course of conduct or usage of trade.

7. Partial Invalidity. The unenforceability or invalidity of any provision of this Agreement shall not affect the enforceability or validity of any other provision herein, and the invalidity or unenforceability of any provision of any loan document related to the Obligations to any person or circumstance shall not affect the enforceability or validity of such provision as it may apply to other persons or circumstances.

8. Applicable Law and Venue. This Agreement has been delivered in the State of Texas and shall be construed in accordance with the laws of that State. It is performable by Pledgor in the county or city of Bank’s address set out above and Pledgor expressly waives any objection as to venue in any such location. Wherever possible each provision of this Agreement shall be interpreted in such manner as to be effective and valid under applicable law, but if any provision of this Agreement shall be prohibited by or invalid under applicable law, such provision shall be ineffective to the extent of such prohibition or invalidity, without invalidating the remainder of such provisions or the remaining provisions of this Agreement.

9. Financing Statement. To the extent permitted by applicable law, a carbon, photographic or other reproduction of this Agreement or any financing statement covering the Collateral shall be sufficient as a financing statement, and Bank is authorized to file this Agreement or any other financing statements it determines to be necessary or prudent.

THIS WRITTEN AGREEMENT AND ANY OTHER DOCUMENTS EXECUTED IN CONNECTION HEREWITH REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly executed by their duly authorized representatives as of the date first above written.

Exhibit 6

LETTER AGREEMENT

Dear David:

I am pleased to advise you that the Board of Directors of Independent Bank Group, Inc. (the “Company”), has on the date of this notice granted to you a total of 12,000 shares (the “Shares”) of common stock of the Company (the “Common Stock”) under and pursuant to the Independent Bank Group, Inc. Stock Grant Plan (the “Plan”), a copy of which is attached hereto. These shares are being issued to you in consideration of services rendered by you to the Company and/or the Company’s subsidiary, Independent Bank.

These shares are subject to restriction on transfer and are subject to forfeiture as set forth in the Plan. By signing below, you agree to be bound by the terms of the Plan and the restrictions set forth therein. In addition, in consideration of the grant of the Shares, you agree as follows:

You must execute and deliver this Letter Agreement to the Company within thirty days in order to receive the Shares allocated to you. Upon receipt of an executed copy of this Letter Agreement, the Company will issue a certificate evidencing the number of Shares. The Company shall retain the certificate until the restrictions are no longer applicable.

ACCEPTED AND AGREED to as of January 1, 2009.

Exhibit 7

INDEPENDENT BANK GROUP, INC.

2013 EQUITY INCENTIVE PLAN

RESTRICTED STOCK AGREEMENT

1. Agreement to Grant Restricted Stock. Subject to the conditions described in this agreement (the “Restricted Stock Agreement”) and in the Independent Bank Group, Inc. 2013 Equity Incentive Plan (the “Plan”), Independent Bank Group, Inc., a Texas corporation (the “Company”), hereby agrees to grant to David R. Brooks (“Participant”) all rights, title and interest in the record and beneficial ownership of Twenty-Five Thousand Six Hundred (25,600) shares (the “Restricted Stock”) of common stock, $0.01 par value per share, of the Company (“Common Stock”). This Award of Restricted Stock shall be effective as of the date (the “Grant Date”) of approval by the Committee. The Grant Date is April 8, 2013. All capitalized terms not otherwise defined herein shall have the meanings set forth in the Plan, the terms of which are incorporated herein by reference.

2. Vesting.

(a) Vesting Schedule. Subject to the satisfaction of the terms and conditions set forth in the Plan and this Restricted Stock Agreement, Participant shall vest in his rights under the Restricted Stock and the Company’s right to the return and reacquisition of such shares shall lapse with respect to the Restricted Stock according to the following schedule and conditions, provided the Participant is then employed by the Company and/or one of its Subsidiaries on such vesting date:

(i) twenty percent (20%) of the Restricted Stock (rounded to the nearest whole number of shares) shall vest on the first anniversary of the Grant Date;

(ii) twenty percent (20%) of the Restricted Stock (rounded to the nearest whole number of shares) shall vest on the second anniversary of the Grant Date;

(iii) twenty percent (20%) of the Restricted Stock shall vest on the third anniversary of the Grant Date;

(iv) twenty percent (20%) of the Restricted Stock shall vest on the fourth anniversary of the Grant Date; and

(v) twenty percent (20%) of the Restricted Stock shall vest on the fifth anniversary of the Grant Date.

(b) Change in Control.

(i) Subject to Section 9(a)(iv) of the Plan, upon the consummation of a Change in Control, any of the Restricted Stock held by Participant that is then unvested and not previously forfeited at the time of such Change in Control shall immediately become vested provided such Participant is continuously employed by the Company or its Subsidiaries through such date.

(c) Certain Terminations of Employment.

(i) All unvested shares of Restricted Stock shall immediately become vested and no longer be subject to restriction upon a termination of employment due to the death or Disability of the Participant, by the Participant for Good Reason, or by the Company not for Cause.

(d) Forfeited Restricted Stock. For the sake of clarity, references to Restricted Stock does not include any previously forfeited Restricted Stock.

3. Forfeiture. Except as provided in Section 2(c) in the event of Participant’s termination of employment by the Company or by Participant for any other reason whatsoever, the unvested portion of the Restricted Stock held by Participant at that time shall immediately be forfeited and required by the Company.

4. Issuance and Transferability.

(a) Registration and Restricting Legend. Upon grant, the Restricted Stock granted hereunder shall be registered in the name of Participant and, unless and until such Restricted Stock vest, shall be left on deposit with the Company, or in trust or escrow pursuant to an agreement satisfactory to the Company, until such time as the restrictions on transfer have lapsed. If the Restricted Stock are represented by certificates, such certificates shall be marked with the following legend:

“The shares represented by this certificate have been issued pursuant to the terms of the Independent Bank Group, Inc. 2013 Equity Incentive Plan and may not be sold, pledged, transferred, assigned or otherwise encumbered in any manner as is set forth in the terms of the Restricted Stock Agreement dated April 8, 2013.”

(b) Book Entry Form. If the shares are held in book entry form, then such entry will reflect, in a manner sufficient to effect in a legally enforceable form, that such shares of Restricted Stock are subject to the restrictions of this Restricted Stock Agreement and the Plan.

(c) Stock Power. Participant will deliver to the Company a stock power, in substantially the form as Exhibit A attached hereto or such form as required by the Company, endorsed in blank, with respect to each Award of Restricted Stock.

(d) Release of Restrictions. Upon vesting of any portion of the shares of Restricted Stock and satisfaction of any other conditions required by the Plan or pursuant to this Restricted Stock Agreement, the Company shall promptly either issue a stock certificate, without such restricted legend, for any shares of the Restricted Stock that have vested, or, if the shares are held in book entry form, the Company shall remove the notations on the book form for any shares of the Restricted Stock that have vested.

(e) Prohibition on Transfer. Until restrictions lapse, the Restricted Stock shall not be transferable. No right or benefit hereunder shall in any manner be liable for or subject to any debts, contracts, liabilities, or torts of Participant. Any purported assignment, alienation, pledge, attachment, sale, transfer or other encumbrance of the Restricted Stock, regardless of by whom initiated or attempted, prior to the lapse of restrictions shall be void and unenforceable against the Company. If, notwithstanding the foregoing, an assignment, alienation, pledge, attachment, sale, transfer or other encumbrance of the Restricted Stock is effected by operation of law, court order or otherwise, the affected Restricted Stock shall remain subject to the risk of forfeiture, vesting requirement and all other terms and conditions of this Restricted Stock Agreement. In the case of Participant’s death or Disability, Participant’s vested rights under this Restricted Stock Agreement (if any) may be exercised and enforced by Participant’s guardian or legal representative.

5. Ownership Rights. Subject to any reservations, conditions or restrictions set forth in this Restricted Stock Agreement and/or the Plan, upon grant to Participant of the Restricted Stock, Participant shall be entitled to all voting rights applicable to the Restricted Stock and the right to currently receive dividends during the Restricted Period. In the event of forfeiture of shares of Restricted Stock, the Participant shall have no further rights with respect to such Restricted Stock.

6. Reorganization of the Company. The existence of this Restricted Stock Agreement shall not affect in any way the right or power of the Company or its stockholders to make or authorize any or all adjustments, recapitalizations, reorganizations or other changes in the Company’s capital structure or its business; any merger or consolidation of the Company; any issue of bonds, debentures, preferred or prior preference stock ahead of or affecting the Restricted Stock or the rights thereof; the dissolution or liquidation of the Company, or any sale or transfer of all or any part of its assets or business, or any other corporate act or proceeding, whether of a similar character or otherwise.

7. Certain Restrictions. By executing this Restricted Stock Agreement, Participant acknowledges that he will enter into such written representations, warranties and agreements and execute such documents as the Company may reasonably request in order to comply with the securities law or any other applicable laws, rules or regulations, or with this Restricted Stock Agreement or the terms of the Plan.

8. Amendment and Termination. This Restricted Stock Agreement or the Plan may be amended or terminated in accordance with the terms of the Plan.

9. Taxes and Withholdings.

(a) Tax Consequences. The granting, vesting and/or sale of all or any portion of the Restricted Stock may trigger tax liability. Participant agrees that he shall be solely responsible for any such tax liability. Participant is encouraged to contact his tax advisor to discuss any tax implications which may arise in connection with the Restricted Stock.

(b) Withholding. Participant acknowledges that the vesting of Restricted Stock granted pursuant to this Restricted Stock Agreement, the making of an election under Section 83(b) of the Code and the vesting and payment of any accrued dividends may result in federal, state or local tax withholding obligations. Participant understands and acknowledges that the Company will not deliver shares of Common Stock or make any payment of accrued dividends until it is satisfied that appropriate arrangements have been made to satisfy any tax obligation under this Restricted Stock Agreement or the Plan and agrees to make appropriate arrangements suitable to the Company for satisfaction of all tax withholding obligations. Further, Participant hereby agrees and grants to the Company the right to withhold from any payments or amounts of compensation, payable in cash or otherwise, in order to meet any tax withholding obligations under this Restricted Stock Agreement or the Plan. As such, if the Company requests that Participant take any action required to effect any action described in this Section 9 and to satisfy the tax withholding obligation pursuant to this Restricted Stock Agreement and the Plan, Participant hereby agrees to promptly take any such action.

(c) Section 83(b). Participant understands that any election under Section 83(b) of the Code with regard to the Restricted Stock must be made within thirty (30) days of the Grant Date and that, in the event of such election, Participant will so notify the Company in writing on or before such date.

10. No Guarantee of Tax Consequences. The Company, Board and Committee make no commitment or guarantee to Participant that any federal, state or local tax treatment will apply or be available to any person eligible for benefits under this Restricted Stock Agreement and assumes no liability whatsoever for the tax consequences to Participant.

11. Confidentiality.

(a) Confidential Information in General. The Participant has and will have access to and participate in the development of or be acquainted with confidential or proprietary information and trade secrets related to the business of the Company and its subsidiaries and affiliates (the “Companies”), including but not limited to (i) business plans, operating plans, marketing plans, bid strategies, bid proposals, financial reports, operating data, budgets, wage and salary rates, pricing strategies and information, terms of agreements with suppliers or customers and others, customer lists and customer information, credit files, software programs, reports, correspondence, tapes, discs, tangible property and specifications owned by or used in Company’s business, operating strengths and weaknesses of the Companies’ officers, directors, employees, agents, suppliers and customers, (ii) information pertaining to future developments such as, but not limited to, research and development, future marketing, products, distribution, delivery or merchandising plans or ideas, and potential new distribution or business locations, and (iii) other tangible and intangible property, which are used in the business and operations of the Companies but not made publicly available (the “Confidential Information”); provided that the term Confidential Information shall not include information that is available or known to persons or entities outside of the Company otherwise than as a result of a breach of a confidentiality agreement. By this Restricted Stock Agreement, the Participant agrees that he or she is being provided with access to Confidential Information to which he or she has not previously had access.

(b) Assignment. The Participant hereby assigns to the Company, in consideration of his employment, all Confidential Information that may be developed by the Participant at any time during the term of this Restricted Stock Agreement, whether or not made or conceived during working hours, alone or with others, which related, directly or indirectly, to businesses or proposed businesses of the Companies, and the Participant agrees that all such Confidential Information shall be the exclusive property of the Companies. The Participant shall establish and maintain written records of all such Confidential Information with respect to inventions or similar intellectual property for the benefit of the Companies and shall execute and deliver to the Companies any specific assignments or other documents appropriate to vest title in such Confidential Information in the Companies or to obtain for the Companies legal protection for such Confidential Information. Notwithstanding anything to the contrary in this paragraph, the Participant shall be entitled to retain possession of any daily journal which the Participant may make reflecting the Participant’s personal log and notes. The Participant will furnish a copy of any retained daily journal to the Company as requested.

(c) Nondisclosure. The Participant shall not disclose, use or make known for his or another’s benefit any Confidential Information of the Companies or use such Confidential Information in any way except in the best interests of the Companies in the performance of the Participant’s duties under this Restricted Stock Agreement.

(d) Continuing Obligations. The obligations of the Participant under this Section 11 shall survive the termination of the Participant’s employment and the expiration or termination of this Restricted Stock Agreement.

12. Return of Company’s Property. Immediately upon termination of the Participant’s employment with the Company, the Participant shall deliver to the Company all Confidential Information, documents, correspondence, notebooks, reports, computer programs, names of full-time and part-time employees and consultants, and all other materials and copies thereof (including computer discs and other electronic media) relating in any way to the business of the Company in any way obtained by the Participant during the period of his employment with the Company. Immediately upon termination of the Participant’s employment with the Company, the Participant shall deliver to the Company all tangible property of Company in the possession of the Participant, including without limitation, telephones, facsimile machines, computers, leased automobiles and credit cards. The obligations of the Participant under this Section 6 shall survive the termination of the Participant’s employment and the expiration or termination of this Restricted Stock Agreement.

13. Noncompetition and Nonsolicitation.

(a) Noncompete. In consideration for (i) the grant to the Participant by the Company, (ii) the provision of Confidential Information, and (iii) the execution of this Restricted Stock Agreement by the Company, and ancillary to the otherwise enforceable agreements in this Restricted Stock Agreement (including Section 1 of this Restricted Stock Agreement), for a period of two (2) years following the termination of the Participant’s employment with the Companies for any reason (the “Noncompetition Period”), the Participant will not, directly or indirectly, without the written consent of the Board of Directors of the Company, own, manage, operate, control, be employed by in the same or in a similar manner to which he or she is employed by the Companies, consult with or participate in or be connected with any entity owning or having financial interest in, whether direct or indirect, a business entity which is in the same line or lines of business as and competes with the Business of the Companies (as defined below), if such business has a branch or other office of any kind located within fifteen (15) miles of any branch or office of the Companies, which the parties stipulate is a reasonable geographic area because of the scope of the Companies’ operations and the Participant’s employment with the Company. For purposes of this Section 13(a), each of the following activities, without limitation, shall be deemed to constitute proscribed activities during the Noncompetition Period: to engage in, work with, have an interest in (other than interests of less than 1% in companies with securities traded on a nationally recognized stock exchange or interdealer quotation system), advise, consult, manage, operate, lend money to (other than

interests of less than 1% in companies with securities traded on a nationally recognized stock exchange or interdealer quotation system), guarantee the debts or obligations of, or permit one’s name or any part thereof to be used in connection with an enterprise or endeavor, either individually, in partnership or in conjunction with any person or persons, firm, association, company or corporation, whether as principal, director, agent, shareholder, partner, employee, consultant or in any other manner whatsoever. The Participant may not avoid the purpose and intent of this Section 13(a) by engaging in conduct within the geographically limited area from a remote location through means such as telecommunications, written correspondence, computer generated or assisted communications, or other similar methods. “Business of the Companies” shall mean the commercial banking business conducted by the Companies as of the date of this Restricted Stock Agreement.

(b) Nonsolicitation. For a period of one (1) year following the date of termination, the Participant will not, directly or indirectly, (i) solicit for employment, or advise or recommend any entity to employ or solicit for employment, any person who is, or at any time during the Noncompetition Period was, an employee of the Company, or (ii) solicit the banking business of, or conduct any banking business with, any Restricted Customer of the Company. For purposes of this Restricted Stock Agreement, “Restricted Customer” means any individual, corporation, limited liability company, association, partnership, estate, trust, or any other entity or organization to which the Companies marketed, attempted to or actually promoted or provided products or services to at any time during the one (1) year immediately prior to the Participant’s last day of employment, and with respect to which the Participant has participated in any efforts related to the marketing, negotiation or provision of products or services, had contact with or supervised employees who had contact with, or received Confidential Information about, within the one (1) year immediately prior to Employee’s last day of employment. This Section 13(b) is geographically limited to wherever any Restricted Customer can be found or is available for solicitation or to do business with, which the parties stipulate is a reasonable geographic area because of the scope of the Companies’ operations and the Participant’s employment with the Company. The Participant may not avoid the purpose and intent of this Section 13(b) by engaging in conduct within the geographically limited area from a remote location through means such as telecommunications, written correspondence, computer generated or assisted communications, or other similar methods.

(c) Continuing Obligations. Notwithstanding any other provision of this Restricted Stock Agreement, the obligations of the Participant under this Section 13 shall survive the termination of the Participant’s employment and the expiration or termination of this Restricted Stock Agreement until the end of the Noncompetition Period.

(d) Reasonable and Necessary. The Participant agrees that the above covenants are reasonable and necessary agreements for the protection of the business interests covered in the fully enforceable, ancillary agreements set forth in this Restricted Stock Agreement.

14. Severability. In the event that any provision of this Restricted Stock Agreement is, becomes or is deemed to be illegal, invalid, or unenforceable for any reason, or would disqualify the Plan or this Restricted Stock Agreement under any law deemed applicable by the Board or the Committee, such provision shall be construed or deemed amended as necessary to conform to the applicable laws, or if it cannot be construed or deemed amended without, in the determination of the Board or the Committee, materially altering the intent of the Plan or this Restricted Stock Agreement, such provision shall be stricken as to such jurisdiction, the Participant or this Restricted Stock Agreement, and the remainder of this Restricted Stock Agreement shall remain in full force and effect.

15. Terms of the Plan Control. This Restricted Stock Agreement and the underlying Award are made pursuant to the Plan. Notwithstanding anything in this Restricted Stock Agreement to the contrary, the terms of the Plan, as amended from time to time and interpreted and applied by the Committee, shall govern and take precedence.

16. Governing Law; Venue. This Restricted Stock Agreement shall be construed in accordance with (excluding any conflict or choice of law provisions of) the laws of the State of Texas to the extent federal law does not supersede and preempt Texas law. Venue for any action to enforce the provisions of this Restricted Stock Agreement shall lie solely in the state and federal district courts located in Collin County, Texas. The parties hereby

submit to the exclusive jurisdiction of the courts of the State of Texas located in McKinney, Texas, or the federal courts of the United States located in the Northern District of the State of Texas in respect of any dispute relating to this Restricted Stock Agreement or to the transactions contemplated hereby. The parties irrevocably waive, to the fullest extent permitted by law, any objection that they may now or hereafter have to the personal and subject matter jurisdiction of such courts to resolve any such dispute or to venue in McKinney, Texas, including an objection based on forum non conveniens.

17. Consent to Electric Delivery; Electronic Signature. Except as otherwise prohibited by law, in lieu of receiving documents in paper format, Participant agrees, to the fullest extent permitted by law, to accept electronic delivery of any documents that the Company may be required to deliver (including, but not limited to, prospectuses, prospectuses supplements, grant or award notifications and agreements, account statements, annual and quarterly reports, and all other forms of communications) in connection with this and any other Award made or offered by the Company. Electronic delivery may be via a Company electronic mail system or by reference to a location on a Company intranet to which Participant has access. Participant hereby consents to any and all procedures the Company has established or may establish for an electronic signature system for delivery and acceptance of any such documents that the Company may be required to deliver, and agrees that his electronic signature is the same as, and shall have the same force and effect as, his manual signature.

[signature blanks follow]

Executed: April 8, 2013.

Accepted: April 8, 2013.

EXHIBIT A

Assignment Separate from Certificate

INSTRUCTIONS: PLEASE DO NOT FILL IN ANY BLANKS OTHER THAN THE SIGNATURE LINE. THE PURPOSE OF THIS ASSIGNMENT IS TO ENABLE THE COMPANY TO EXERCISE ITS “REPURCHASE OPTION” SET FORTH IN THE RESTRICTED STOCK AGREEMENT WITHOUT REQUIRING ADDITIONAL SIGNATURES ON THE PART OF THE PURCHASER.

FOR VALUE RECEIVED,                                          hereby sells, assigns and transfers unto Independent Bank Group, Inc., a Texas corporation (the “Company”),                                               (            ) shares of common stock of the Company represented by Certificate No.                      and does hereby irrevocably constitute and appoint                                         , or his designee or successor, as attorney to transfer the said stock on the books of the Company with full power of substitution in the premises.

Dated:             , 20        .

Exhibit 8

WARRANT

TO PURCHASE SHARES OF COMMON STOCK

OF

INDEPENDENT BANK GROUP, INC.

PURCHASE PRICE PER SHARE: $55.00

THIS CERTIFIES that, for value received, DAVID R. BROOKS (the “Registered Owner”) is entitled, subject to the terms and conditions of this Warrant, until the Expiration Date (as defined herein), to purchase 7,272 shares of the common stock, $1.00 par value (the “Common Stock”), of Independent Bank Group, Inc. (the “Company”) from the Company at $55.00 per share.

Section 1. Exercise. The purchase rights represented by this Warrant are exercisable at the option of the Registered Owner, in whole or in part, at any time prior to 5:00 pm (CST) on December 23, 2018 (the “Expiration Date”). The Expiration Date is subject to amendment pursuant to Sections 8 and 9 hereof.

Section 2. Method of Exercise. Subject to the provisions hereof, the Warrant may be exercised by delivery of this Warrant to the Company with the exercise form duly executed and payment of the purchase price (in immediately available funds) for the shares purchased.

Section 3. Company’s Covenants as to Common Stock. Shares of Common Stock deliverable on the exercise of this Warrant shall, at delivery, be fully paid and non-assessable.

Section 4. Limited Rights of Owner. This Warrant does not entitle the Registered Owner to any voting rights or other rights as a shareholder of the Company, or to any other rights whatsoever except the rights herein expressed. No dividends are payable or will accrue on this Warrant or the shares purchasable hereunder until, and except to the extent that, this Warrant is exercised.

Section 5. Transfer/Assignability. This Warrant shall not be assignable or otherwise transferable except by will or by the laws of decent and distribution or pursuant to a qualified domestic relations order.

Section 6. Recognition of Registered Owner. Prior to due presentment for registration of transfer of this Warrant, the Company may treat the registered owner as the person exclusively entitled to receive notices and otherwise to exercise rights hereunder.

Section 7. Adjustment of Shares Subject to Purchase. If the Company, by stock dividend, split, reverse split, or reclassification of shares, changes as a whole the outstanding Common Stock into a different number or class of shares, then:

(1) the number and class of shares so changed shall, for the purposes of this Warrant, replace the shares outstanding immediately prior to the change; and

(2) the Warrant purchase price in effect, and the number of shares purchasable under this Warrant, immediately prior to the date upon which the change becomes effective, shall be adjusted proportionately (with the purchase price being adjusted to the nearest cent). Irrespective of any adjustment or change in the Warrant purchase price or the number of shares purchasable under this Warrant, the Warrants theretofore issued may continue to express the Warrant purchase price per share and the number of shares purchasable as were expressed in the Warrants when initially issued.

On the happening of an event requiring an adjustment of the Warrant purchase price or the shares purchasable hereunder, the Company shall forthwith give written notice to the Registered Owner stating the adjusted Warrant purchase price and the adjusted number and kind of securities or other property purchasable hereunder resulting from the event and setting forth in reasonable detail the method of calculation and the facts upon which the calculation is based. The board of directors of the Company, acting in good faith, shall determine the calculation.

Section 8. Capital Call. Should any governmental agency which has jurisdiction over the Company’s subsidiary, Independent Bank, McKinney, Texas (the “Bank”) require the Bank to increase its capital, the Expiration Date shall be amended to the date set forth by the directors of the Bank at their sole discretion or as set forth by the governmental agency mandating the increase of capital. Failure to exercise the Warrant prior to such amended Expiration Date (whether as set forth herein or as amended pursuant to a regulatory agency mandated increase in capital) shall cause the termination of the Warrant and the holder hereof shall have no further right to exercise the Warrant.

Section 9. Merger or Dissolution. In case of a merger or consolidation in which the shareholders of the Company are entitled to receive consideration, or a voluntary or involuntary dissolution, liquidation, receivership or winding up of the Company is at any time proposed, the Company shall, to the extent feasible, give at least 10 days’ written notice to the Registered Owner prior to the record date as of which holders of Common Stock will be entitled to receive consideration or distributions as a result of the proposed transaction. Such notice shall contain: (1) the date on which the transaction is to take place; (2) the record date as of which holders of Common Stock will be entitled to receive consideration or distributions as a result of the transaction; (3) a brief description of the transaction; (4) a brief description of the consideration or distributions to be made to holders of Common Stock as a result of the transaction; and (5) an estimate of the fair value of the consideration or distributions. In the event of such transaction, the Expiration Date shall be amended to be the effective date of such transaction. Failure to exercise the Warrant prior to such amended Expiration Date shall cause the termination of the Warrant and the holder hereof shall have no further right to exercise the Warrant.

Section 10. Method of Giving Notice; Extent Required. Notices shall be given in writing by hand delivery, electronic mail, or by first class mail, postage prepaid, addressed to the Registered Owner at the address appearing in the records of the Company. No notice to a holder of this Warrant is required except as specified in Sections 7 and 8 above.

Section 11. Access to Information. The Company will provide an opportunity to any Registered Owner of this Warrant to ask questions of management of the Company and to obtain information to the extent the Company has the same in its possession prior to any exercise of the Registered Owner’s rights to purchase Common Stock under this Warrant. Requests for information and any other questions concerning the business and affairs of the Company should be directed to the Chairman of the Board of Directors of the Company at its main business offices.

Section 12. Shareholder Agreements. Any shares of Common Stock acquired pursuant to the exercise of the Warrant shall be subject to the Amended and Restated Shareholders Agreement, as amended, and the Drag Along and Tag Along Rights Agreement to which the Registered Owner is a party.

Section 13. No Registration. This warrant and any securities acquired upon the exercise of this warrant have not been registered under: (a) the Securities Act of 1933, as amended, in reliance upon the exemptions from registration provided in sections 3 and 4 of such act; or (b) any state securities laws in reliance upon applicable exemptions thereunder. This warrant and any securities acquired upon the exercise of this warrant must be acquired

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for investment only for the account of the investor and may not be sold or transferred in the absence of an effective registration of them under such act and all other applicable securities laws or an opinion of counsel (or such other evidence) acceptable to the company or its representatives that such sale or transfer would not violate applicable securities laws or regulations. At the time this warrant is exercised, the holder is entitled to receive updated financial information on the Company.

Dated effective December 23, 2008

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EXERCISE FORM

The undersigned hereby: (1) irrevocably subscribes for                      shares of the Company’s Common Stock pursuant to this Warrant, and encloses payment of $                     therefor; (2) requests that a certificate for the shares be issued in the name of the undersigned and delivered to the undersigned at the address below; and (3) if such number of shares is not all of the shares purchasable hereunder, that a new Warrant of like tenor for the balance of the remaining shares purchasable hereunder be issued in the name of the undersigned and delivered to the undersigned at the address below.

Exhibit 9

April 2, 2013

Sandler O’Neill & Partners, L.P.

1251 Avenue of the Americas, 6th Floor

New York, New York 10020

The undersigned, an executive officer, director, shareholder and/or proposed shareholder of Independent Bank Group, Inc., a Texas corporation (the “Company”), understands that Sandler O’Neill & Partners, L.P., as representative of one or more underwriters, (the “Representative”), proposes to enter into an Underwriting Agreement (the “Underwriting Agreement”) with the Company providing for the public offering of shares (the “Shares”) of the Company’s common stock, $0.01 par value per share (the “Stock”). In recognition of the benefit that such an offering will confer upon the undersigned as an executive officer, director and/or shareholder of the Company, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the undersigned agrees with the Representative that, during a period of 180 days from the date of the Underwriting Agreement (the “Lock-up Period”), the undersigned will not, without the prior written consent of the Representative, directly or indirectly, (i) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant for the sale of, or otherwise dispose of or transfer any shares of the Stock or any securities convertible into or exchangeable or exercisable for shares of the Stock, whether now owned or hereafter acquired by the undersigned or with respect to which the undersigned has or hereafter acquires the power of disposition, or file any registration statement under the Securities Act of 1933, as amended, with respect to any of the foregoing or (ii) enter into any swap or any other agreement or any transaction that transfers, in whole or in part, directly or indirectly, the economic consequences of ownership of the Stock, whether any such swap or transaction is to be settled by delivery of Stock or other securities, in cash or otherwise.

Notwithstanding the foregoing, the undersigned may (i) transfer the undersigned’s shares of the Stock (a) as a bona fide gift or gifts or charitable contributions, provided that the donee or donees agree to be bound in writing by the restrictions set forth herein, (b) pursuant to the exercise by the undersigned of, or the vesting of shares of Stock held by the undersigned pursuant to, options or other rights to acquire or receive shares of the Stock or any security of the Company convertible into shares of the Stock that have been granted by the Company pursuant to any equity incentive, stock rights or stock option plan described in the Registration Statement on Form S-1 of the Company registering the offer and sale of the Shares (each, a “Plan”), where the shares of the Stock received upon any such exercise are held by the undersigned, individually or as fiduciary, in accordance with the terms of this Lock-Up Agreement, (c) to the Company in connection with a cashless or “net” exercise of any options or other rights to acquire shares of the Stock or any security of the Company convertible into shares of the Stock that have been granted by the Company pursuant to any Plan, (d) to any trust, family limited partnership or similar entity for the direct or indirect benefit of the undersigned or the immediate family of the undersigned, provided that the trustee of the trust, general partner of the family limited partnership or similar person, as the case may be, agrees to be bound by the restrictions set forth

herein, (e) by testate or intestate succession, provided that each transferee agrees to be bound in writing by the restrictions set forth herein, (f) if the undersigned is an entity, transfers to the limited partners, beneficial interest owners, members or stockholders as part of a distribution, or to any corporation, partnership or other business that is its affiliate of the undersigned, provided that each transferee agrees to be bound in writing by the restrictions set forth herein, (g) that the undersigned acquires on the open market after the date of the Underwriting Agreement, (h) held in an discretionary trading account maintained by a broker-dealer for the benefit of a person other than the undersigned and over which the undersigned may be deemed to have the power of disposition, or (i) with the prior written consent of the Representative; provided that, in the case of any transfer, distribution or sale pursuant to this clause (i), no filing under Section 16(a) of the Exchange Act of 1934, as amended (the “Exchange Act”), during the Lock-Up Period shall be required or shall be voluntarily made in connection therewith (other than a filing that reports solely one or more acquisitions of shares of the Stock); and (ii) enter into a written trading plan with respect to shares of the Stock designed to comply with Rule 10b5-1 under the Exchange Act, provided that no sales are made pursuant to such trading plan during the Lock-up Period. For purposes of this Lock-Up Agreement, “immediate family” shall mean any relationship by blood, marriage or adoption, not more remote than first cousin. The undersigned now owns and, except as contemplated by one or more of clauses (i)(a) through (i) and (ii) above, for the duration of this Agreement will own the undersigned’s Shares, free and clear of all liens, encumbrances and contractual obligations existing as of the date hereof which could foreseeably result in a disposition of the undersigned’s Shares during the Lock-Up Period, except for those (if any) disclosed in an appendix to this letter. The undersigned also agrees and consents to the entry of stop transfer instructions with the Company and its transfer agent and registrar against the transfer of the undersigned’s Shares, except in compliance with the foregoing restrictions. In furtherance of the foregoing, the Company is hereby authorized to decline to make or authorize any transfer of securities of the Company if such transfer would constitute a violation or breach of this Lock-Up Agreement.

The undersigned understands that the Company, the Representative and the other underwriters party to the Underwriting Agreement are relying upon this Lock-Up Agreement in proceeding toward consummation of the Offering. The undersigned represents and warrants that the undersigned has full power and authority to enter into this Lock-Up Agreement. The undersigned further understands that this Lock-Up Agreement is irrevocable and agrees that the provisions of this Lock-Up Agreement shall be binding also upon the successors, assigns, heirs and personal representatives of the undersigned.

If the Underwriting Agreement does not become effective, if the Underwriting Agreement (other than the provisions thereof which survive termination) shall terminate or be terminated prior to payment for and delivery of the Shares to be sold thereunder (other than any shares of Common Stock subject to the underwriters’ over-allotment option) or, if the undersigned is not a director, officer or shareholder of the Company at the date of this Lock-Up Agreement and does not purchase any Shares in the proposed directed share program in connection with the public offering of the Shares, the undersigned shall be released from all obligations under this Lock-up Agreement. Notwithstanding anything herein to the contrary, this Lock-up Agreement shall automatically terminate and be of no further effect as of 4:00 p.m. Eastern Time on April 8, 2013 if a closing for the offering of the Shares has not yet occurred as of that time.

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This Lock-up Agreement shall be governed by and construed in accordance with the laws of the State of New York.

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Exhibit A to Lock Up Agreement

David Brooks

962,093 shares of unregistered stock are pledged.