A cousin marriage is a marriage where the spouses are cousins (i.e. people with common grandparents or people who share other fairly recent ancestors). The practice was common in earlier times, and continues to be common in some societies today, though in some jurisdictions such marriages are prohibited.

Is it wrong to marry your relatives?

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.

What is it called when someone marries their cousin?

2. The most commonly used word would be incest, although technically, incest refers to sex between (close) relatives. However, since a marriage is usually supposed to be consummated (meaning the partners in the marriage do have sex), the word is also applied to marriage.