In Illinois, marrying your first cousin is generally illegal, but the law carves out two narrow exceptions. Second cousins and more distant relatives, however, can marry without restriction under state law.
First‑Cousin Marriage: Mostly Prohibited
Illinois’ Marriage and Dissolution of Marriage Act (750 ILCS 5/212) lists “a marriage between cousins of the first degree” as a prohibited relationship. That means the average first‑cousin couple cannot obtain a valid Illinois marriage license unless they meet one of two special conditions.
The statute declares that a first‑cousin marriage is not prohibited if:
- Both parties are 50 years of age or older, or
- At the time of the marriage license application, a licensed physician certifies that one party is “permanently and irreversibly sterile,” and that certificate is filed with the county clerk.
If neither condition is met, an Illinois clerk will typically refuse to issue a license for a first‑cousin marriage, and any such union performed elsewhere may not be recognized as valid in Illinois.
Second Cousins and Distant Relatives
Illinois law does not outlaw marriages between second cousins or cousins of more distant degrees. As long as the parties are otherwise eligible to marry—meeting age, consent, and other standard requirements—the state treats these unions the same as any other marriage. This distinction reflects the legislature’s focus on close genetic ties when it comes to first‑degree cousins.
Out‑of‑State and Same‑S*x Marriages
Illinois is picky about recognizing first‑cousin marriages from other states or countries. If the couple would not qualify to marry in Illinois—because neither is 50 plus nor permanently sterile—the state may treat the out‑of‑state union as void. That matters for things like inheritance, immigration, and benefits.
The same rule applies to same‑sex couples: Illinois allows first‑cousin marriages only if both partners are 50 or older, or if one is medically certified as permanently sterile. The law does not distinguish based on the couple’s gender, focusing instead on age and reproductive status.
Practical Considerations
Because Illinois ties cousin‑marriage legality to age or sterility, couples considering this step should consult both a family‑law attorney and a physician if needed.
They should also check with the county clerk’s office before applying for a license, since forms and documentation can vary slightly by county. Outside of first‑degree cousins, Illinois largely stays out of family‑marriage decisions, giving second cousins and more distant relatives a clear path to legal marriage.
SOURCES:
- https://www.bnd.com/news/state/illinois/article284904242.html
- https://mywaynecountynow.com/is-it-illegal-to-marry-your-cousin-in-illinois-heres-what-the-law-says/
