Kin Groups and Descent. Ache society is not divided into descent groups, clans, sibs, or sections. Traditional band composition was flexible but often included sets of sibs (both sexes), their husbands, and some affinal kin. Close male relatives helped each other in club fights (see "Social Organization"), and female relatives cooperated to some extent in child rearing. Kinship was considerably less important in determining daily economic and social interaction than is the case for most small-scale societies. Informants consistently report strong alliances and residence with individuals described as "friends," having no close kin connection. Affinal ties were strong as long as the marriage lasted, but faded rapidly after separation. Sibling sets containing more than three surviving adult full siblings were rare, but often very cohesive and politically important when they existed.