Bi-fraternal polyandrous marriages were more common than tri-fraternal or quadri-fraternal polyandry, because the latter forms of marriage were often characterized by severe familial tensions (reference missing).Different mechanisms were employed to reduce the number of sons within a household, such as making one son a celibate monk, or sending away a son to become an adoptive bridegroom to a family without male children.Another reason for polyandry is that the mountainous terrain makes some of the farm land difficult to farm, requiring more physical strength.
Concern over which children are fathered by which brother falls on the wife alone.
She may or may not say who the father is because she does not wish to create conflict in the family or is unsure who the biological father is.
Historically the social system compelled marriage within a social class.
When the People's Republic of China annexed Tibet, political systems in many regions of Tibet remained unchanged until, between 19, political reforms changed the land ownership and taxation systems.
If the widower remarried another woman, two conjugal families would have been created, leading to the eventual partition of the estate.
Bigenerational polyandry, whereby the father shared a wife with his son, was therefore the solution to avoid this problem.In traditional inheritance rules, only males had rights over the land, but where there were no males to inherit them, the daughters had the right over the corporation’s land.To maintain the familial estate unit, the daughters would share a bridegroom who will move matrilocally (as opposed to the patrilocal principle where the brides move into the husband's family) and become a member of his wife's family.Bigenerational polygamy was present as an application of the mono-marital principle.Let us consider a family in which the mother died before the son was married.Another kind of marriage, although uncommon, is the "polygynous marriage".