Laws regarding first-cousin marriage in the United States As of February 2014, 24 U.S. states prohibit marriages between first cousins, 19 U.S. states allow marriages between first cousins, and 7 U.S. states allow only some marriages between first cousins. Six states prohibit first-cousin-once-removed marriages.

Is it legal to marry your first cousin in Australia?

The Guidelines on the Marriage Act 1961 for Marriage Celebrants states, “An uncle may marry his niece and an aunt may marry her nephew” and ” Cousins may marry each other”. Under Australian law its illegal for a man to marry his grandmother, mother, sister or half-sister, daughter or granddaughter.

Why is it wrong to marry your cousin?

Marrying a cousin is usually considered a bad idea, because inbreeding can lead to harmful genetic conditions. But paradoxically, in some societies, marrying a related spouse is linked to having more surviving children, research suggests.