It is said that the Kirihara clan descended from the Oba clan, which descended from the Kamakura clan, one of Bando Hachi Heishi (the Eight Taira clans of the East), and the Kaminaga clan descended from the Fujiwara clan.
桐原氏は坂東八平氏のひとつ鎌倉氏の流れを汲む大庭氏の血筋であり、神長氏は藤原氏であるという。