Several states of the United States prohibit cousin marriage. As of February 2014, 24 U.S. states prohibit marriages between first cousins, 19 U.S. states allow marriages between first cousins, and seven U.S. states allow only some marriages between first cousins.

When did dating your cousin become illegal?

Cousin marriage were legal in ancient Rome from the Second Punic War (218–201 BC), until it was banned by the Christian emperor Theodosius I in 381 in the West, and until after the death of Justinian (565) in the East, but the proportion of such marriages is not clear.

Can first cousins have healthy babies?

The vast majority of children of first cousins are healthy and do not have problems due to their parents relatedness. It is important to keep in mind that even for an unrelated couple, there is an approximately 2-3% chance that their child is born with a birth defect, genetic syndrome, or disability.