Kin Groups and Descent. Okiek groups vary in the relative importance they place on lineages and clans as kinship groups (see "Social Organization"). For Kaplelach and Kipchornwonek, patrilineally defined lineages are most important: they figure in landholding and residence, the arrangement of marriages, and legal matters. Matrilateral and affinal relations are important emotionally, in the recruitment of work groups, and on ceremonial occasions; they can also affect residential and legal decisions. For some Okiek groups farther north, such as Kapchepkendi and Piik aap Oom, the patrician is far more important as a social unit and is central in defining land rights.
Kinship Terminology. Kipchornwonek and Kaplelach Okiek reckon kinship in a way that resembles an Omaha system, but their cousin terminology is not the same as the canonical Omaha model. Mother's brothers, all their children, and all children of one's father's sisters are called maama. The children of one's mother's sisters are regarded as siblings ( tuupca ), but are called lianashe, a term related to the Maasai word for "sister," enkanashe.