Tex. Health & Safety Code § 166.035
The following persons may execute a directive on behalf of a qualified patient who is younger than 18 years of age:
Acts 1989, 71st Leg., ch. 678, Sec. 1, eff. Sept. 1, 1989. Renumbered from Sec. 672.006 by Acts 1999, 76th Leg., ch. 450, Sec. 1.03, eff. Sept. 1, 1999.