Kin Groups and Descent. The Somali system of patrilineal descent embraces the whole nation in a genealogical grid and claims ultimate descent from the Qurayshitic lineage of the prophet Mohammed. At the level of residential groupings, a set of patrilineally related kinsmen will form the nucleus of a kin group, to which other people are joined by ties of affinity or matrilaterality. For practical purposes, the genealogical depth of a residential kin group rarely goes beyond four or five generations; however, in matters such as feuding and payment of blood-wealth, the range of agnatically related kinsmen who are involved is greatly expanded.
Kinship Terminology. Parental siblings are referred to by bifurcate-collateral terms. Cousin terms are either Sudanese or Hawaiian. Where the latter prevails, it is usually for reasons of politeness, just as any stranger of approximately the same age as Ego may be addressed as "brother/sister." Seniority is emphasized in the use of intragenerational terms. Many intergenerational terms are used self-reciprocally, so that, for instance, a man addresses his son as "father."