Connecticut bans first-cousin marriages, effective Oct. 1

Connecticut will ban marriages between first cousins beginning Oct. 1, after a bipartisan, unanimous vote in the General Assembly and a signature from Gov. Ned Lamont. The measure addresses concerns about the higher risk of birth defects associated with cousin unions and reflects a shift in policy that brings Connecticut in line with other states that restrict such marriages.

As passed earlier this year, the bill states: "No person may knowingly marry such person's first cousin." Republican Rep. Devin Carney told the Connecticut Post that the move followed an acknowledgement that Connecticut was one of the few states not to ban the practice. "We looked at it and saw we were sort of an outlier state that didn't ban it. Science shows that procreation between first cousins increases the chances of birth defects," he said. The law will not penalize or invalidate marriages that already exist under the prior law, and it will not affect marriages that occurred before Oct. 1, according to Newsweek.

Connecticut’s existing statute already bars marriage within several degrees of kinship, including parent, grandparent, child, grandchild, sibling, and certain relatives by marriage, but did not explicitly address first cousins. The new measure explicitly prohibits first-cousin marriages and adds Connecticut to the list of about 25 states that ban the practice. Neighboring states such as New Jersey, New York and Vermont still permit cousin marriages, while others—such as Alabama, California, Colorado, Florida, Georgia, Maryland, Massachusetts, New Mexico, North Carolina, Rhode Island, South Carolina, Tennessee and Virginia—also ban some or all cousin unions. States with partial restrictions include Arizona, Illinois, Indiana, Maine, Utah, and Wisconsin, and South Dakota has broader prohibitions that extend to sexual relations and cohabitation.

Supporters say the law protects potential offspring from higher risks of congenital disabilities and reflects a public health approach supported by scientific study. Critics argue that it intrudes on private family decisions and could complicate relationships for people who had marriages valid under previous law. Democratic Rep. Darren Jernigan, who championed similar measures in Tennessee, faced pushback there from lawmakers who argued about state interest and constitutional considerations; some opponents in other states view the moves as government overreach, while supporters contend public health is a legitimate government concern.

Lamont’s office said the bill becomes law on Oct. 1 and that Connecticut’s policy aligns with a national trend toward restricting first-cousin marriages. The development comes as Connecticut, a firmly Democratic-leaning state, continues to reevaluate family law in light of evolving scientific and public health considerations. The decision also arrives amid ongoing nationwide conversations about the balance between personal liberty and state interest in safeguarding health outcomes.