The first Oe appeared in 'Nihon shoki' was the eldest son of Emperor Keitai, Magari no Oe (later, Emperor Ankan), who was active during the first half of the 6th century.
日本書紀によると、6世紀前期にいた継体天皇の長子の勾大兄（まがりのおおえ、安閑天皇）が大兄として初めて現れている。