In order to separate political trends from reasons why society should preferentially value families, a specific definition of the family is needed. The definition of a family varies according to the political climate of the times. Currently domestic living units that are not devoted to childrearing seek to be defined as families in order to qualify for financial and employment benefits awarded married couples and childrearing families. A married couple has been regarded as the precursor of a childrearing family. Defining a family is further complicated by the fact that a family is not a living unit but is a network of relationships.
Family relationships can be biological, adoptive, foster, step, and in-law.
Although family members live together while children are young, families continue to exist in kin relationships throughout life. Family relationships also do not depend primarily on financial or friendship considerations. The purpose of the family is to prepare children for productive lives that advance the evolution of homo sapiens sapiens . In this light parenthood is the social institution that prepares and sustains individuals for life in society. The essential core of parenthood is mutual attachment bonding.