All the former Imperial Family members were the male descendants of the fourth Fushiminomiya Imperial Prince Sadatsune, who was the head of the successive Imperial hereditary family since the Muromachi period, and were also descendants of the third Emperor, Emperor Suko of the Northern Court during the period of the Northern and Southern Courts.
旧皇族は、すべて室町時代以来続く世襲親王家の筆頭であった伏見宮の第4代伏見宮貞常親王の男系子孫にあたり、南北朝時代の北朝第3代崇光天皇の末裔でもある。