A Cuiva is born into a social world that is rigorously ordered: within the immediate community of the band, everyone is a relative who shares a specific kinship link with oneself. The classification even covers the entire social universe, as it extends to every known member of other bands; in fact, only non-Indians, who in any case are not part of humanity, are outside this classification system. The system is Dravidian in many of its main characteristics, and the terms are classificatory in the widest sense. The entire society is ordered into only twelve categories of kin (or even six categories, each subdivided by sex) and over only three successive generations, because the system also equates alternate generations, thus providing siblings and cousins with Ego's own generation but also within Ego's grandparents' and grandchildren's generations. As kinship defines and imposes rules of appropriate behavior, it identifies which goods to give or exchange, who gets respect, with whom to joke, and so on. Perhaps most important, there is within each generation a clear distinction between the cross cousins one can and must marry and the categories of siblings and parallel cousins with whom marriage is forbidden. In short, the system of kinship organizes the social world as a complete network of kin relations that ensures the maintenance and reproduction of society. But the system does not really extend beyond this network: the Cuiva never trace lines of descent, do not form social groups based on common descent, and generally demonstrate a remarkable lack of genealogical memory.
Every adult in society has a spouse, with only the rare exceptions of the recently divorced and elderly widowed. Men marry for the first time around the age of 26, whereas women should marry just before puberty. Residence after marriage follows the rule of uxorilocality; it is the young man who leaves the shelter of his parents to go and live with his new wife and her parents. The couple, "those who sleep in the same hammock," represent the minimal group in society. The next-larger unit is called "those who sleep under the same shelter" and is normally composed of a couple, their daughters with their husbands, and all unmarried children. These are the people who always live together, producing and sharing food as a unit, and who often literally share the same palm roof, use the same fire, and cook and eat together.
These groups are only rarely isolated from the rest of the society, however, and are normally joined to a larger unit (which can be called "local group" but for which the Cuiva themselves have no special name) that includes from ten to forty individuals and is formed by the lasting association of a few shelters. There is no jurally precise mode of affiliation, but shelters joining to form a local group usually include some very close relatives—typically, brothers and sisters who have been separated by the rule of uxorilocal residence. The joining together of all local groups forms the band, or the union of what the Cuiva call "one people" or "our people." The rights of membership in the band are not well defined, and although they are at times expressed by the rather vague idea of a common origin, membership is in fact dependent on integration at the level of the smaller units (being married and part of a residential group) and on the general consensus within the band, which seems to be contingent mostly on the length of time a person has spent with the group.