The family in Japan is called kazoku (家族?) in Japanese. It is basically composed of a couple as is the family in other societies. The Japanese family is based on the line of descent and adoption. Ancestors and offspring are linked together by an idea of family genealogy, or keizu, which does not mean relationships based on mere blood inheritance and succession, but rather a bond of relationship inherent in the maintenance and continuance of the family as an institution.
In any given period of history, all family members have been expected to contribute to the perpetuation of the family, which is held to be the highest duty of the member.
A great number of family forms have existed historically in Japan, from the matrilocal customs of the Heian.
As official surveys conducted during the early years of the Meiji dynasty demonstrated, the most common family form during the Edo or Tokugawa period was characterized by patrivirilocal residence, stem structure, patrilineal descent and patrilineal primogeniture, so a set of laws were promulgated institutionalizing this family pattern, beginning with the "Outline of the New Criminal Law" in 1870. In 1871, individuals were registered in an official family registry (戸籍 koseki?).
In the early twentieth century, each family was required to conform to the ie (家?, household) system, with a multigenerational household under the legal authority of a household head. In establishing the ie system, the government moved the ideology of family in the opposite direction of trends resulting from urbanization and industrialization. The ie system took as its model for the family the Confucian-influenced pattern of the upper classes of the Tokugawa period.