When Takauji ASHIKAGA helped the Emperor Komyo to the throne and the Emperor Godaigo escaped to Yoshino, Sanenatsu rendered service together with his father to the new emperor and, as his elder brother, Saneyo TOIN, who was the heir, joined the Southern Court and was disinherited, Sanenatsu, who was the second son, inherited the Toin family.
足利尊氏が光明天皇を擁立して後醍醐天皇が吉野に逃れた際に、実夏は父とともに新帝に仕えるが、嫡男である兄の洞院実世が南朝(日本)に参加したために廃嫡となり、次男の実夏が洞院家を継承する事になった。