Kin Groups and Descent. Kinship-based groups include the family, the household, the house-owning group, the garden-owning group, the cooperating or fishing group, and the joint family. With regard to those groups beyond the Family and household, rights to house sites on Luangiua and Pelau are held by house-owning groups that trace their ancestry through females. Men, as sons and brothers of these women, also have interests in the house sites. The garden-owning group is also formed around females: daughters Inherit their rights to taro gardens from their mothers, and they may decide to divide their garden land. The cooperating or fishing group is an informal group of closely related males, often brothers and their sons, who fish together and cooperate informally in other activities. The members of a joint Family usually are related through patrilineal descent from an ancestor who lived about six generations earlier. In some cases, nonagnates (e.g., the offspring of a member's sister) can be incorporated into the joint family. Members of the joint Family share rights to land planted with coconut trees, most notably the islets others than Luangiua and Pelau. Joint families have leaders, usually the oldest males. The patrilineal principles followed with regard to joint families apparently developed in response to the increased importance of the copra trade in the late nineteenth century. There are many land disputes in present-day Ontong Java, and tracing genealogies is important in litigating and adjudicating them.
Kinship Terminology. Ontong Java uses a Hawaiian-type, or generational, kinship terminology system, with one notable exception: the mother's brother and his sister's Children address one another by a reciprocal term, lamoku, and their relationship entails special obligations.