It is said that for many years his parents had prayed for a blessing before an image of the Kannon Buddhist, deity of mercy, so that they were finally blessed with a baby who was Gien, and under Emperor Tenmu's command he was brought up along with the imperial princes at Okamoto no miya Palace.
父母が長年観音菩薩に祈願して授かり、天武天皇により親王とともに岡本宮で養育されたという。