The total of 12 families were collectively called "Shichizoku goro," including the initial seven families that were unable to succeed the main family and thus supported the main family as branch families, being in charge of military affairs, and five families served as small feudal lords selected as senior vassals in charge of governmental affairs.
元々は跡継ぎと成れずに支族として宗家を支え、軍務を担当していた7家に、重臣に抜擢して政務を担当させた小領主たち5家を加えた12家の総称である。