Thyestes

Pelops's son and Atreus brother, with whom he was a rival to the throne of Mycenae. Thyestes seduced Atreus wife Aerope, and made her steal Atreus golden fleece.

When the people of Mycenae decided the owner of the fleece would be king, Thysestes took the throne. Zeus then reversed the course of the son, and Thyestes had to abdicate, only to be succeeded and banished by his brother.

When Atreus discovered his wife had been unfaithful with Thyestes, he called his brother back, and served him his two sons for dinner. Thyestes then laid the famous curse on Atreus and his house.

Thyestes later raped his own daughter Pelopia on suggestion by the Oracle in Delphi, and she gave birth to Aegisthus, the evil man who would seduce Clytemnestra and kill Agamemnon.