It is believed that the Kobayakawa clan was established by the descendants of Sanehira DOHI who was one of the aides of MINAMOTO no Yoritomo and made a good showing in the Genpei War (war between Minamoto clan and Taira clan), Shigehira was the fourth generation down from Sanehira and that the name of Kobayakawa was taken from Hayakawa, a place-name in Dohi-go Village, Izu, home ground of his feud.
小早川氏は、源頼朝の側近の一人で源平合戦で活躍した土肥実平の後裔と伝えられ、茂平は実平より数えて四代目にあたり、小早川の名は土肥氏の本拠地である伊豆の土肥郷にある早川の地名を採ったものとされる。