The biological basis of family is explained due to the existence of two sexes and reproduction. Further, it is the natural answer to human sexual urges. The institution of the family is to be explained in terms of biological factor-the existence of two sexes and the sexual character of reproduction in the human species. It appears as a natural answer to the human sexual drive, a phenomenon solidly based in the biology of the human organism. Family provides legitimacy to all these biological activities with the support of marriage. The family is characterised by its limited size. Because of this characteristic feature, family is identified as a primary group. It may include parents and their unmarried children or parents and their married as well as unmarried children. The bonds that tie together these limited number of members with limited common interests are the outcome of emotional factors such as love, mutual affection and solicitude. This emotional basis of the family makes it an ideally suitable primary social group in every society.