In "Sonpi Bunmyaku" (a text compiled in the fourteenth century that records the lineages of the aristocracy), it is written that he was the son of TAIRA no Shigemori, who was the younger brother of TAIRA no Sadamori, and the younger brother of TAIRA no Kanetada (Kazusa no suke (Assistant Governor of Kazusa Province).
『尊卑分脈』では平貞盛の弟陸奥守平繁盛の子で平兼忠（上総介・出羽守従五位上）の弟とある。