Query: What clans were most regional clans' chiefs also a member of?
Context: In time, they amassed enough manpower, resources and political backing in the form of alliances with one another, to establish the first samurai-dominated government. As the power of these regional clans grew, their chief was typically a distant relative of the Emperor and a lesser member of either the Fujiwara, Minamoto, or Taira clans. Though originally sent to provincial areas for a fixed four-year term as a magistrate, the toryo declined to return to the capital when their terms ended, and their sons inherited their positions and continued to lead the clans in putting down rebellions throughout Japan during the middle- and later-Heian period.