Marriage. Traditional marriage among the Nasioi was ideally between bilateral cross cousins; thus a boy would marry a girl who was at once his mother's brother's and father's sister's daughter. Even if such a genealogical relationship did not obtain, the pattern was of continuing exchange between two clans, on a model of balanced reciprocity that operated in other realms of social life. Child betrothal was common, often negotiated between the mothers of the children. Exchange of food and other valuables was supposed to balance; there was no bride-price or dowry as ordinarily defined. If a widow remarried, either she or her intended new husband might be expected to make a prestation to the clan of her deceased husband. Polygyny was rare, practiced only by unusually industrious men. Residence after marriage was uxorilocal, and divorce was easy. Cross-cousin marriage, polygyny, and child betrothal came under early attack from missionaries and are not normative today. Because educated young people are more likely to seek out others of comparable accomplishments, modern marriages may be contracted between Nasioi and other groups, including other Papua New Guineans and Europeans.
Domestic Unit. Households traditionally consisted of a married couple and immature children. Sometimes an aged parent or other relative might join a kinsman's household. The nuclear family household continues to be a norm; in the 1960s and thereafter adolescent boys (either relatives or friends) might establish their own group household, since it was considered inappropriate for such youth to dwell under the same roof with parents who were still sexually active.
Inheritance. Much of a deceased person's property was consumed or destroyed during funeral rituals, so that there was little to inherit. Land rights were inherited matrilineally in the first instance, but other factors such as a major prestation of food from the deceased's children to his clansmen might prevail. Today, cash-crop trees or money normally pass from parents of either sex to their children, but the conflict between tradition and demands of the new economy increases the likelihood of disputes.
Socialization. While mothers had primary responsibility for child care, fathers, older siblings, and the entire settlement took an active interest. Life-cycle events, such as a first trip to the garden, were often the occasion for ceremonial exchanges, which varied considerably as to scale and elaboration. Often the child's "aunts," who were members of a different clan, performed sometimes ribald songs or dances to mark the event; they were then given food, betel nuts, or other valued items as compensation. A girl's menarche might be marked by a short period of seclusion, followed by a feast with singing and dancing. This practice was discouraged by missionaries and, in the 1960s, was usually confined to the daughters of ambitious men. There were no ceremonies to mark a boy's adolescence. Today, formal education has replaced most, if not all, traditional observances.