SDCL § 22-22A-2: Incest--Prohibited sexual contact--Felony.

Any persons, eighteen years of age or older, who knowingly engage in a mutually consensual act of sexual penetration with each other:

(1) Who are not legally married; and

(2) Who are within degrees of consanguinity within which marriages are, by the laws of this state, declared void pursuant to § 25-1-6;

are guilty of incest. Incest is a Class 5 felony.