In traditional Muong society there was a strict hierarchical separation between the nobles and the commoners. Each village or hamlet headman belonged to one of the four dominant clans, namely, Dinh, Quach, Bach, and Hoang. They had the hereditary prerogative of ruling or administering the unit. Clan exogamy is followed strictly. The commoners, on the other hand, mostly carried the patronym "Bui." This is not a clan, but is something like a caste. Intermarriage among the Bui is common, as they are not necessarily relatives; intrahamlet marriages are frequent. Marriage is strictly forbidden in a patrilineage. Each lineage is divided into two branches, the elder and the younger. Lineage unity is maintained by a lineage head chosen from among those conversant with usage and custom. When any member of a lineage faces any difficulty, others tend to help without being asked. The beneficiary receives the assistance as a matter of right. During marriages, funerals, and other rites, gifts are made willingly to the household and the work is shared. Such reciprocal exchanges are more frequent among the commoners than among the nobility.