The Family name Koremune implies that the Koremune clan descended from the Hata clan and in respect of the members of the clan whose names included a kanji letter "忠" (meaning "faith") as tsuji (distinctive character used in the names of all people belonging to a single clan or lineage), there are two explanations, one is that they were from families branched out from Emperor Shomu and the other is that they were from families branched out from Emperor Daigo.
惟宗姓である事から秦氏の後裔であり、忠を通字とする惟宗氏に皇別の聖武天皇説・醍醐天皇説の二流がある。