Twin brothers Atreus and Thyestes were rivals for the throne of Mykenai (Mycenae). When Atreus was awarded the throne, Thyestes seduced his wife in order to gain possession of a golden ram which would secure him the kingdom. Atreus was exiled but, upon his return, reclaimed the throne and expelled Thyestes. He was, however, still hungry for revenge and so invited his brother back, murdered his two young sons and served them up as a meal.
Later Thyestes' adult son Aigisthos (Aegisthus) avenged this crime by murdering Atreus, but Atreus' sons--Agamemnon and Menelaus--drove him from the kingdom.