A family is a group of individuals related to one another by blood ties, marriage, or adoption who form an economic unit, the adult members of which are responsible for the upbringing of children. All known societies involve some form of family system, although the nature of family relationships is widely variable across cultures and throughout history. While in modern societies the main family form is often considered the nuclear family (a couple and their dependent children), a variety of extended family relationships (including grandparents, aunts, uncles, and cousins) are also frequently found and play important roles in individuals' lives. The family serves as a primary agent of socialisation, providing emotional support, care, and a sense of belonging for its members. It also plays a crucial role in the transmission of cultural norms, values, and traditions across generations.