He was a descendant of Emperor Bidatsu. He was a son of Chinu no ōkimi (Prince Chinu, 茅渟王) by Kibitsuhime no ōkimi (Princess Kibitsuhime, 吉備姫王). Empress Kōgyoku was his elder sister from the same parents. Chinu was a son of Prince Oshisaka hikohito no ōe, whose father was the Emperor Bidatsu. He had at least three consorts including his Empress, Hashihito no Himemiko (Princess Hashihito), the daughter of Emperor Jomei and his sister Empress Kōgyoku. In the 3rd year of Kōgyoku-tennōs reign (皇極天皇三年), the empress abdicated; and the succession (senso) was received by her younger brother. Shortly thereafter, Emperor Kōtoku is said to have acceded to the throne (sokui).Titsingh, pp. 47–48; Brown, p. 266; Varley, p. 44; a distinct act of senso is unrecognized prior to Emperor Tenji; and all sovereigns except Jitō, Yōzei, Go-Toba, and Fushimi have senso and sokui in the same year until the reign of Emperor Go-Murakami.
He was a descendant of Emperor Bidatsu. He was a son of Chinu no ōkimi (Prince Chinu, 茅渟王) by Kibitsuhime no ōkimi (Princess Kibitsuhime, 吉備姫王). Empress Kōgyoku was his elder sister from the same parents. Chinu was a son of Prince Oshisaka hikohito no ōe, whose father was the Emperor Bidatsu. He had at least three consorts including his Empress, Hashihito no Himemiko (Princess Hashihito), the daughter of Emperor Jomei and his sister Empress Kōgyoku In the 3rd year of Kōgyoku-tennōs reign (皇極天皇三年), the empress abdicated; and the succession (senso) was received by her younger brother. Shortly thereafter, Emperor Kōtoku is said to have acceded to the throne (sokui).Titsingh, pp. 47–48; Brown, p. 266; Varley, p. 44; a distinct act of senso is unrecognized prior to Emperor Tenji; and all sovereigns except Jitō, Yōzei, Go-Toba, and Fushimi have senso and sokui in the same year until the reign of Emperor Go-Murakami.