Family is a set of people related by blood, marriage or some other agreed-upon relationship, or adoption, who share the primary responsibility for reproduction and caring for members of society.
Definition Two:
Family is a group of individuals related to one another by blood ties, marriage, or adoption. Members of families form an economic unit, the adult members of which are responsible for the upbringing of children. While all societies involve some form of family, the form the family takes is widely variable. In modern industrial societies, the main family form is the nuclear family, although a variety of extended family relationships is also found.