Sibling

A sibling is a person who shares at least one parent with another person. In humans, siblings may be biological, adopted, or connected through marriage or guardianship. The term covers full siblings (sharing both parents) and various other relations such as half-siblings (sharing one parent), step-siblings (through a parent's remarriage), and adoptive or foster siblings.

Genetic relatedness varies: full siblings typically share about half of their genetic material, while half-siblings share about a quarter on average. However, the exact degree of relatedness can differ due to recombination and parental genetic contribution. Sibling relationships can form early in life and continue across the lifespan, influencing social development, cooperation, competition, and support networks.

In many cultures, siblings play important roles in caregiving, resource sharing, and family dynamics. Birth order, age gaps, and sex composition can shape interactions, but findings on personality and behavior are mixed.

Etymology and usage: The word sibling originated in English as a gender-neutral term for a brother or sister, derived from kinship-related roots. It is commonly used in anthropology, psychology, social science, and biology to describe kin relationships beyond gendered terms.

Related terms include kinship, family, half-sibling, step-sibling, and adoptive relationships.