It is illegal to marry your first cousin in South Dakota. Both full and half first cousin marriages are expressly prohibited by state law, with a blanket ban and no exceptions.
What the Law Says
- South Dakota prohibits marriage between close relatives, including parents and children, siblings, uncles and nieces, aunts and nephews, and first cousins—whether full or half blood.
- These restrictions apply regardless of adoption status or whether the relationship arose through adoption.
- There are no exceptions for age, genetic counseling, or infertility.
- First cousins once removed (your cousin’s child or your parent’s cousin) and more distant relatives are allowed to marry.
State Marriage Application
South Dakota does not specifically ask on the marriage license whether the couple are cousins, but the law requires couples to affirm that no prohibited relationship exists.
Table
| Relationship type | Marriage allowed? |
|---|---|
| First cousins | No |
| First cousins (half blood) | No |
| First cousins once removed | Yes |
| Second cousins | Yes |
| Uncles/aunts–nieces/nephews | No |
South Dakota’s cousin marriage ban has been in place since the 1860s and remains absolute, making it illegal to marry your first cousin under any circumstances.
Sources
(https://dataminingdna.com/can-first-cousins-marry-in-south-dakota/)
(https://findalawyerinsd.com/pages/areas-marriage)
(https://en.wikipedia.org/wiki/Cousin_marriage_law_in_the_United_States)
(https://marriage.uslegal.com/state-marriage-laws/south-dakota/)
(https://sdlegislature.gov/Statutes/25-1-6)
