Marrying your first cousin is illegal in Missouri under state law. The relevant statute, Missouri Revised Statutes Section 451.020, explicitly prohibits unions between first cousins, declaring them presumptively void, and bars officials from issuing licenses for such marriages.
Prohibited Relationships
Missouri bans marriages between close relatives, including parents/children, grandparents/grandchildren, siblings (whole or half-blood), uncles/aunts and nieces/nephews, and first cousins of any degree. This stems from consanguinity rules aimed at genetic and social concerns, with first cousins sharing about 12.5% DNA on average.
Second cousins, first cousins once removed, and more distant kin face no restrictions and can legally wed.
Legal Consequences
Attempting a first-cousin marriage in Missouri renders it invalid—no common-law recognition applies. Out-of-state marriages where cousin unions are legal may gain recognition, but courts scrutinize validity; cohabitation and relations remain permitted despite the ban. No criminal penalties attach solely to the marriage, but related fraud (e.g., false applications) could trigger misdemeanor charges.
Exceptions and Variations
No waivers exist for age, infertility, or other factors—unlike states like California allowing first cousins over 65 or one sterile partner. Half-cousins require county clerk clarification, as statutes cover half-blood ties broadly. Same-sex cousin marriages follow the same prohibitions if first-degree.
Out-of-State Considerations
Missouri sometimes honors valid foreign marriages, but first-cousin ones risk nullification for benefits, inheritance, or divorce. Couples often travel to permissive states like Arizona or Iowa.
Practical Advice
Verify kinship via family trees before applying for licenses—clerks reject prohibited pairs upfront. Consult a family law attorney for inheritance or immigration impacts. While 2026 brings no changes, track legislative updates via Missouri Revisor of Statutes.
This clear ban aligns Missouri with 24 other states restricting first-cousin marriage, prioritizing public policy over individual choice.
SOURCES :
- https://www.avvo.com/legal-answers/is-there-any-state-that-allows-half-cousin-marriag-5077437.html
- https://getordained.org/state-marriage-laws/missouri
