In the context of human society, a family (from ) is a group of people affiliated by consanguinity (by recognized birth), affinity (by marriage), or co-residence and/or shared consumption (see Nurture kinship). Members of the immediate family may include, singularly or plurally, a spouse, parent, brother, sister, son and/or daughter. Members of the extended family may include grandparents, aunts, uncles, cousins, nephews nieces and/or siblings-in-law. In most societies, the family is the principal institution for the socialization of children. As the basic unit for raising children, anthropologists generally classify most family organization as matrifocal (a mother and her children); conjugal (a husband, his wife, and children; also called the nuclear family); avuncular (for example, a grandparent, a brother, his sister, and her children); or extended (parents and children co-reside with other members of one parent’s family). Sexual relations among the members are regulated by rules concerning incest such as the incest taboo. “Family” is used metaphorically to create more inclusive categories such as community, nationhood, global village and humanism. Genealogy is a field which aims to trace family lineages through history. Family is also an important economic unit studied in family economics.