Kin Groups and Descent. The local totemically named patrilineal clan is the exogamous unit among the Foi and varies considerably in size. Smaller unnamed "lineages" consisting of a man and his adult sons are the units of marriage negotiation, though the local clan is the unit of exogamy and bride-wealth distribution. Descent is patrilineal. Orphaned children are sometimes claimed by their mother's brother, the clan of "true origin" in the Foi view.
Kinship Terminology. To the extent that this is a useful characterization, the Foi have an Iroquois-type terminology. Adults often address each other by their teknonyms if not otherwise related. In the past, reciprocal food-sharing names (special personal names used by those who shared food Without obligation to do so) were common as modes of address, and children of people who shared such a name often called each other by their parents' food-sharing name.