Cousin marriage is a legally or socially recognized marriage between two cousins, or persons sharing a common ancestor.

In some jurisdictions and cultures, such marriages are legal and actively encouraged, while in others they are regarded as incest and prohibited. Still other cultures merely tolerate marriages between first cousins, but at the same time these unions are not encouraged.

Any random two people have a common ancestor and are cousins to some degree, but most people don't know their common ancestor. Usually, unless otherwise qualified, "cousin" means first cousin, someone with whom one shares one pair of grandparents.

History

In earlier times, and still today in some cultures, it was relatively common for cousins to get married. Since people tended not to move far from their place of birth, the closest eligible spouse was often a cousin. As a result, it has been estimated that up to 80% of all marriages in history have been between second cousins or closer. Cousin marriage has often been chosen as a way of keeping cultural values intact through several generations, as well as ensuring the compatibility of spouses residing in an alien environment. Finally, marrying a cousin is also a way of keeping land and property in the family. Traditionally, such arranged marriages have been facilitated by the extended family.