In old Tibet before 1951, in order to prevent the dispersion of property, there were marriages such as polyandry, polygamy, brother co-wife, and sister co-husband. The situation of polygamy mostly occurs in upper-class families, namely, lords and chieftains who expand their sphere of influence through Tibet weddings . Before 1951, there were many polygamous noble families mainly due to political and economic reasons. Because through marriage, they can consolidate their property status. The wives of such families were usually from different chieftains or tribes. There are also polygamous marriages existing in civilian families. The husbands usually cohabit with his wife’s sisters after marrying his wife, thus forming a de facto husband and wife relationship. In this kind of family, the sisters share a husband together, and their statuses are equal.