Marriage. In the past, polygynous marriage was preferred, and many men had two wives, with a few very wealthy men having three or four. Polyandry also occurred, though with considerably less frequency. Under European influence, all marriages are now monogamous. Cross-cousin marriage was preferred, with a mother's brother's daughter's daughter or father's sister's daughter's daughter the most desirable mate for a man. This preference meant that men often married a woman one generation removed from themselves. Divorce was easy and frequent, with the wife always retaining custody of the children. Postmarital residence is matrilocal, though marriages within a hamlet were common, and therefore men often did not have to relocate to a new one. For the Lesu, incest was the most serious norm violation, so various restrictions and taboos operated to control contact between men and women whose relations would be considered incestuous.
Domestic Unit. The nuclear family household is the basic domestic unit. It consists of the husband, wife, unmarried daughters, and sons under the age of 9 or 10. Boys older than 9 or 10, unmarried men, and men whose wives are pregnant or nursing live in the men's house, though much of their daily activity centers on the household. In polygynous families, each wife and her children usually occupied a separate dwelling.
Inheritance. Although inheritance of knowledge and material objects is preferentially matrilineal, in practice the desires of the owner of the property or the family are more influential than the clan rules.
Socialization. Infants are indulged by their mothers and fathers and developmental events such as the first tooth are marked by feasts. Children are observers of and participants in the daily lives of the adults in their household and in the community. Very early on, a clear distinction is made between boys and girls, with the two kept separate. Age groups for boys are encouraged but not for girls. In the past, boys age 8 to 11 underwent an elaborate initiation rite, lasting eight months with an additional two months for preparations. The rite included seclusion in a specially built dwellng, circumcision, feasting, dancing, speech making, and an exchange of wealth. The initiation rite was always accompanied by the malanggan rite during which the malanggans were displayed and then destroyed. Under Roman Catholic influence, the duration of the initiation rite was shortened and it was followed by instruction at the mission. First menstruation was marked by feasting and ritual bathing which signified that the girl was now an adult and ready to marry.