Kin Groups and Descent. The bilateral kindred of the Pima Bajo typically consists of nuclear families that have increasingly intermarried so that affinal and consanguineal connections have produced a pattern of endogamy. The latent function may be to retain possession within the kin group of sufficient land to assure subsistence production. The pattern may also result from the small size of the intermarrying group. Among the Mountain Pima, nuclear families frequently live on ranchos or small farms, often with extended family in the household or in the parajes. The unification of family groupings through the association of siblings allows for the greatest reciprocity in economic and social terms.
Kinship Terminology. Kinship usage varies considerably among the different segments of Pima society. Generally persons under age 40 and those living in Blanco communities tend to use terminology modeled on the Spanish use. Modification of Pima kinship terminology has occurred in two ways: reduction in the number of kin categories recognized in speech, and extensive substitution of Spanish words for Pima terms. In particular, the bifurcate collateral classification for parents' siblings has been collapsed into a lineal system by applying the same term for relatives previously designated by different words; both mother's and father's sister came to be addressed as tía (Spanish: aunt) rather than by the separate terms indicating age (younger or older) and designating father's or mother's side of family. The same changes hold true for the father's side of the family, with use of the Spanish term tío. Similar changes occur in designations of the child's and grandparental generations.
Fictive Kinship. The custom of selecting cosponsors for various ceremonies, called compadrazgo (ritual coparenthood), has been adopted from Spanish conventions. This institution takes on the manifestations of fictive kinship, replete with all the reciprocal social and economic relationships that characterize kin ties. The most important aspect surrounds the Catholic ritual of baptism, with those for marriage and confirmation generally missing among the Pima. Compadres, as the cosponsors and parents of the sponsored are called, may on occasion be Blancos, but they are more frequently Pima and are usually selected from close blood relatives and affines of the parents. The presence of Pima terms for the male and female compadres may indicate that it overlays an ancient Pima practice, or it may mean that Pima terms have been applied to this institution. The child being sponsored (Pima: vak már; Spanish: ahijado ), calls his or her sponsors padrino and madrina. The parents of the child and the sponsors establish a lifelong relationship involving gift giving and respect; they refer to each other as vak 'dog and vak dáad (in Pima, the reciprocal terms in Spanish being compadre and comadre ). As with their mestizo neighbors, the most important relationship between nuclear families is with compadres.