S.D. Codified Laws § 25-1-6
Current with legislation signed by the governor on or before 3/6/2024
Marriages between parents and children, ancestors and descendants of every degree, and between brothers and sisters of the half as well as the whole blood, and between uncles and nieces, or aunts and nephews, and between cousins of the half as well as of the whole blood, are null and void from the beginning, whether the relationship is legitimate or illegitimate. The relationships provided for in this section include such relationships that arise through adoption.
SDCL 25-1-6