Aegisthus

I. the son of Thyestes, who murdered Atreus and Agamemnon, with whose wife, Clytœmnestra, he lived in incest, and was finally slain by Orestes, Cic. N. D. 3, 38; Ov. R. Am. 161.— Hence, Pompey called Cæsar Ægisthus, on account of his adulterous connection with Mucia, Suet. Caes. 50.