According to the 'Ordinance of the Heir to the Imperial Throne,' the scope of Koshin is stipulated as up to and including the emperor's great-grandchildren (fourth generation); the fifth generation, or great-great-grandchildren, were called princes but not considered to be part of the imperial heritage.
皇親の範囲は、「継嗣令」の規定では天皇の四世孫までが皇親とされ、五世孫は王を称したが皇孫にはあたらないとされた。