Kin Groups and Descent. Igbo society places strong emphasis on lineage kinship systems, particularly the patrilineage, although some Igbo groups, such as the Ohaffia, have a matrilineal descent system, whereas groups like the Afipko Igbo have a double descent system. In all the Igbo groups, one's mother's people remain important throughout one's life.
Kinship Terminology. The umunna, children of one father or a localized patrilineage, is made up of specific compound families, which consist of even more basic matricentric household units of each mother and siblings. The umunna is made up of both male and female cognates of an Igbo man's father's lineage. All blood-related kinship groups are bound in the morality or ethics of umunne, the ritualized spirit of a common mother. Ndi-Umune, or ikwunne, is the term used to describe the mother's agnates.