Genealogically, he is said to have been a son, grandchild, or great grandchild of TAIRA no Sukemori but the root is unclear (he is also said to have been in a line of the Seki family originating from the Taira family).
系譜上は平資盛の子とも孫あるいは曾孫ともされるが、確かな出自は不詳である（平姓関氏の系統ともいう）。