A nephew is your brother's son or your sister's son. If your brother has a baby boy, that child is your nephew. If your sister has a son, he's also your nephew. The relationship works both ways: you become that boy's aunt (if you're female) or uncle (if you're male).

The word also applies to your spouse's siblings' sons. If your husband's sister has a son, that boy is your nephew too, though some people specify by calling him a nephew by marriage.

Nephews can be important people in your life. Some uncles and aunts take their nephews camping, teach them skills, or just enjoy watching them grow up. In families where siblings stay close, nephews often become like younger brothers or even, years later, good friends.

The female equivalent is niece, which refers to your brother's daughter or sister's daughter. Together, nephews and nieces are called your nibling (though most people just say “my nephews and nieces” or “my siblings' kids”). In some cultures and time periods, uncles and aunts played major roles in raising their nephews and nieces, sometimes even adopting them if parents couldn't care for them.