Traditionally, a family is a group of people living together with some shared kinship (such as common ancestors or descendents), marriage, or adoption. However, societies are increasingly accepting variations in which people care for one another, share resources (e.g., food) and divide responsibilities (e.g., household chores) without any kinship ties (e.g., childless and unmarried couples). Families with kinship ties across generations reproduce society via procreation and socialization of children, with the aid of legal, social, and/or religious recognition of family members' rights and obligations.

The predominant family structures in developed countries are nuclear families, couples without children, and single parents with children. Other important contributors to family structures include extended family members and siblings. Two-parent families constituted the majority of households in past decades in most ...