It is said that this family was founded during the Kamakura Period with Toshisada BOJO, who was a son of Tsunetoshi YOSHIDA, but there is another view that the founder was Toshizane BOJO (grandson of Toshisada), who was the eldest son of Sadasuke BOJO, who in turn was the son of Toshisada.
鎌倉時代に吉田経俊の子・坊城俊定を祖として創設されたといわれているが、俊定の子である坊城定資の長男坊城俊実（俊定の孫にあたる）を祖とする説もある。