The son of Thyestes and his daughter Pelopea. Desiring to avenge himself upon his brother Atreus and acting on the advice of the oracle at Delphi, Thyestes consummated an incestuous union with his daughter Pelopia. Shortly afterward, Atreus married Pelopia, not knowing she was his niece. When Aegisthus was born, Atreus accepted him as his own son, not knowing that he had been fathered by Thyestes. Aegisthus later learned his true identity and, urged by Thyestes, killed Atreus. While Agamemnon, king of Mycenae, was away fighting in the Trojan War, Aegisthus became the lover of Queen Clytemnestra. He helped Clytemnestra kill her husband upon his return from Troy. Together with the queen, Aegisthus then ruled Mycenae for seven years. He was later murdered by Agamemnon's son Orestes.