In the Yunnan and Sichuan provinces of China lives a small ethnic group called the Mosuo. Among the Mosuo, romantic and family life are separated into different spheres by design. Children are usually raised in the home of their maternal grandmother with the help of their mother. She may maintain a long-term, monogamous romantic relationship with the father but, unlike in the West, this is considered separate from her role as a mother.H/t Dan Everett.
The role of the biological father is discretionary. There is no word in their language, in fact, for husband or father. A father is allowed, but not required to provide financial support and he is usually permitted to visit the mother and their child(ren) only at night. They call it “Axia” or “walking marriage.” The children’s primary male role models are usually their uncles, who remain under the authority of the children’s grandmother as they live under her roof.
From the Mosuo point of view, separating marriage from the raising of children ensures that the vagaries of romance do not disrupt the happiness and health of the child and its mother. Nor can the father wield power over the mother by threatening to withdraw from the marriage.
Check out this 20 min. documentary on the Mosuo: