A tourist once told me that while on a trip to some country he came across families who exchanged their members for sex regularly. Any children born belong to the mother's family. The bonds within the family were very strong while physical intimacy with other families in the village was arranged by the women themselves.... maybe with the consent of the men. The men did all the outside work while women were mainly engaged in household work.
The concept makes interesting reading though I doubt its reality. Maybe we can adapt.