The HOJO family was a clan with TAIRA no Naokata, a Takamochi line of the Taira clan, as the supposed ancestor, and although the family was the head of the HOJO clan, whose base was the HOJO estate in Izu Province, Tokimasa himself might have represented a collateral line of the head family, according to one theory.
平氏高望流の平直方を祖と称する一族で、伊豆国北条庄を拠点とした北条氏の当主とも言われているが、時政はその傍流であったのではないかとの説もある。