He was son of King Perdiccas III of Macedon. After his father's death in 359 BC he became king, but he was only an infant. Philip II of Macedon, Perdiccas' brother, became his tutor and regent. In that same year Philip II declared himself king of Macedonia, expropriating his young nephew. Amyntas was not judged dangerous enough to be a menace to Philip, who even gave him his daughter Cynane in marriage. The succession of Alexander in 336 BC changed things - he immediately had Amyntas executed.