A marriage is void if one party to the marriage is related to the other as:
(1) an ancestor or descendant, by blood or adoption;(2) a brother or sister, of the whole or half blood or by adoption;(3) a parent’s brother or sister, of the whole or half blood or by adoption; or(4) a son or daughter of a brother or sister, of the whole or half blood or by adoption.
Tex. Fam. Code ยง 6.201
Added by Acts 1997, 75th Leg., ch. 7, Sec. 1, eff. April 17, 1997.