Kayapó kinship is bilateral, and genealogical reckoning is shallow. Owing to continuous fissioning, the Kayapó have relatives in several villages. Besides real kinship, they have a large number of relatives acquired either by adoption or through friendship. Kinship terms establish the relationship of each individual to other individuals in the village. Kayapó must not marry near relatives in the same residential segment. Kinship terminology is of the Omaha type. Nuclear families of an extended family or residential segment, including affinal relations, form a mutual-support unit, in daily life as well as in times of illness.
Important kinship and ceremonial relationships are those between ngêt (mother's father, father's father, and sister's brother) and tabdjuo (daughter's son, son's son, and sister's son) or between kwatui (mother's mother, father's mother, and father's sister) and tabdjuo (daughter's daughter, son's daughter, and brother's daughter). Ngêt and kwatui give their names and ceremonial privileges to their tabdjuo. This institution is one of the most important for the perpetuation of Kayapó society.
Formal friendship relationships are inherited patrilineally but are between nonrelated persons with whom a special relationship of respect and avoidance is maintained. A formal friend plays an important role during certain ceremonies in which he assists his partner, especially during rites of passage.