Looking back further still to the Heian period, in the timeframe following OTOMO no Otomaro and SAKANOUE no Tamuramaro's duties as seii taishogun, taking on the role of seii taishogun was not limited to the Minamoto clan.
古く遡れば平安時代、征夷大将軍に任ぜられた大伴弟麻呂や坂上田村麻呂以来、征夷大将軍の任免は源氏に限らず。