The Reizei family is a sideline of the Nijo branch of the Mikosa line descended from FUJIWARA no Nagaie, the son of FUJIWARA no Michinaga (not to be confused with the Nijo branch of the Five Sekke (Regent) family).
藤原道長の子藤原長家を祖とする御子左流二条派（五摂家の二条家とは別）の庶流。