In Illinois, marriage between first cousins is generally prohibited by law. The Illinois Marriage and Dissolution of Marriage Act (750 ILCS 5/212) specifically lists first cousin marriages among those not allowed in the state.
The Exceptions: When First Cousins Can Marry
However, there are two explicit exceptions to this rule:
- Both Parties Are 50 or Older: If both individuals seeking to marry are at least 50 years old, they are permitted to marry even if they are first cousins.
- Either Party Is Permanently Sterile: If either party can provide a physician’s certificate stating that they are permanently and irreversibly sterile, the marriage is allowed regardless of age.
These exceptions are designed to address concerns about potential genetic risks associated with children born to first cousins, though recent research suggests these risks are often overstated.
Legal Text Reference
The relevant Illinois statute states:
“A marriage between cousins of the first degree; however, a marriage between first cousins is not prohibited if: (i) both parties are 50 years of age or older; or (ii) either party, at the time of application for a marriage license, presents for filing with the county clerk…a certificate signed by a licensed physician stating that the party…is permanently and irreversibly sterile.”
Other Relatives and Prohibitions
Illinois also prohibits marriage between other close blood relatives such as siblings, parents and children, uncles and nieces, and aunts and nephews. These prohibitions are absolute and do not have age or sterility exceptions.
Out-of-State Marriages
If an Illinois resident marries their first cousin in another state where such marriages are legal, Illinois will generally not recognize the marriage unless it meets the same exceptions (age or sterility) required by Illinois law.
Summary Table: First Cousin Marriage in Illinois
| Situation | Is Marriage Legal? |
|---|---|
| Both first cousins under 50, fertile | No |
| Both first cousins 50 or older | Yes |
| Either first cousin is permanently sterile | Yes |
| Other close relatives (siblings, etc.) | No |
Marrying your first cousin in Illinois is illegal unless both parties are at least 50 years old or one is permanently sterile, as certified by a physician. Outside of these exceptions, first cousin marriages are not permitted in the state.
Sources:
- https://en.wikipedia.org/wiki/Cousin_marriage_law_in_the_United_States
- https://www.illinoistimes.com/news-opinion/why-cant-cousins-marry-15982640
- https://www.findlaw.com/state/illinois-law/illinois-annulment-and-prohibited-marriage-laws.html
- https://www.ilga.gov/legislation/ilcs/documents/075000050K212.htm
- https://b100quadcities.com/first-cousin-marriage-chicago-illinois/