Mikael III Atreides was the son of Emperor Mikael II and the brother of Mikael IV, Mikael V and Mikael VI and at least one sister. When his father left the throne and retired in cryogenic suspension in 4670 AG, Mikael III was also with him and he was kept for most of his life. However when he was restored, he deposed his father in 4888 AG and put him in a prison. He was succeeded by his brother, Mikael IV.