Nephew and niece are kinship terms used to describe the children of one's siblings. A nephew is the son of a person's brother or sister, while a niece is the daughter of a brother or sister. For clarity of relation see the basic definition: a nephew is the son of someone's brother or sister and a niece is the daughter of that sibling. From the child's point of view, the adult is an uncle or an aunt.

Kinship degree and genetic relationship

In genetic terms a full sibling’s child is a second-degree relative, typically sharing about 25% of genes with the aunt or uncle. When the parent is a half-sibling, the expected coefficient of relationship drops (commonly about 12.5%). These simple percentages are average estimates used in genetics and family studies, and actual relatedness varies with family history and ancestry.

Variations, names and usage

Different languages and cultures use specific words for maternal and paternal nieces/nephews, and many societies apply informal or honorific titles to relatives and family friends. In everyday speech some people call the children of their cousins “nieces” or “nephews,” though the strict genealogical term for a cousin’s child is first cousin once removed. Older English once used terms such as "sister-son" for a sister's son. Modern English also has proposed gender-neutral alternatives like "pibling" for aunt/uncle.

  • Direct example: the son of your sister = your nephew.
  • Common misuse: cousins' children sometimes called nephews/nieces instead of first cousins once removed; see cousin relationships.
  • In-law relations: children related by marriage may be called nephews/nieces informally.

Beyond naming, the roles of nephews and nieces vary: they may have legal recognition in inheritance or guardianship when closer relatives are absent, they often appear in family narratives and genealogies, and they can hold important social roles in extended-family networks. Cultural practices influence expectations, such as patterns of childcare, mentoring and inheritance.

Understanding the distinction between genealogical definitions and colloquial usage helps avoid confusion. Nephews and nieces are key members of extended families, with both biological and social dimensions that differ across cultures and legal systems.