 Olympias was the daughter of Neoptolemus I, king of the Molossians, an ancient Greek tribe in Epirus, and sister of Alexander I.Her family belonged to the Aeacidae, a well-respected family of Epirus, which claimed descent from Neoptolemus, son of Achilles.Apparently, she was originally named Polyxena, as Plutarch mentions in his work "Moralia", and changed her name to Myrtale prior to her marriage to Philip II of Macedon as part of her initiation into an unknown mystery cult.