Since the time of MINAMOTO no Mitsunaka, Seiwa-Genji served for generations as keishi of the Northern House of the Fujiwara clan (regent family) and actively participated in tashihaiseki (expulsion of other clans from the Imperial Court) by the clan.
清和源氏は源満仲以来、藤原北家（摂関家）の家司として代々仕え、同家による他氏排斥の際には藤原北家の家司として積極的に関与した。