Okla. Stat. tit. 43, § 43-2: Consanguinity

Marriages between ancestors and descendants of any degree, of a

stepfather with a stepdaughter, stepmother with stepson, between

uncles and nieces, aunts and nephews, except in cases where such

relationship is only by marriage, between brothers and sisters of

the half as well as the whole blood, and first cousins are declared

to be incestuous, illegal and void, and are expressly prohibited.

Provided, that any marriage of first cousins performed in another

state authorizing such marriages, which is otherwise legal, is

hereby recognized as valid and binding in this state as of the date

of such marriage.