Niece and nephew
In the language of kinship, a niece is a daughter of a person's sibling, and a nephew is a son of a person's sibling. Conversely, that person is the aunt or uncle of their nibling. The relationship of aunt/uncle to niece/nephew is an example of second-degree relatives, meaning that their coefficient of relationship is 25%. A half-niece is a daughter of a person's half-sibling, half-nephew is a son of a person's half-sibling and they are third-degree relative with 12.5% genetic overlap.