Note: Do not rely on this information. It is very old.
AEgisthus, the mythological son of Thyestes and Pelopea, who, having been adopted as a son by Atreus, seduced Clytemnestra, the wife of Agamemnon, then absent in the Trojan War. On the return of the latter, AEgisthus, with his paramour's assistance, slew him, and reigned in Mycenas for seven years, when he was killed by Orestes. The story furnished AEschylus with a plot for three of his tragedies.