“The family is a historically and geographically diverse social institution which, in principle, designates a social group of people connected by blood, marriage, or adoption. This group of people is characterised by having a common residence, cooperating economically, and overseeing the reproduction and care of its descendants. In spite of the fact that there is no academic consensus on the universal nature of the family, different disciplines—from anthropology to history, by way of sociology, psychology, and demography—have accounted for its importance, stating that the family is the basic social institution or element which forms the backbone of social organisation.”

Reference: Serrano, M. L., & Biglia, B. (2020). Family. In D. T. Cook (Ed.), The SAGE encyclopedia of children and childhood studies. Sage UK.

See also
domestic partnership/marriage
intergenerational relations
family policy