Sec. 7.02. SURVIVING SPOUSE OF RETIREE. (a) On the death of a retiree, the retiree's surviving spouse is entitled to receive an immediate monthly benefit from the fund of 75 percent of the retirement benefit that was being paid to the retiree if the spouse:

(1) was married to the retiree at the time of the retiree's retirement; or

(2) married the retiree after the retiree's retirement and was married to the retiree for at least 24 consecutive months.

(b) For purposes of Subsection (a)(1) of this section, with respect to an informal marriage established in this state, a surviving spouse is considered married to a retiree as of the date a declaration of informal marriage was recorded in accordance with Subchapter E, Chapter 2, Family Code.