The father of Agamemnon, Atreus, was the King of Mycenae. He gave a golden lamb to his wife Aerope. She, however, gave it to her lover – Thyestes, Atreus’ brother. Thyestes persuaded Atreus that the owner of the golden lamb should be the rightful king; and then produced the lamb and so claimed his brother’s throne. To win the throne back, Atreus got his brother to agree to give up the kingdom when the sun moved backwards in the sky. Atreus had arranged this to happen with Zeus, and so became King once again. Thyestes was banished.
After the banishment, Atreus learned of the adultery being committed between his wife and his brother. As revenge, he invited his brother and his two eldest nephews back to Mycenae. There, under the guise of rebuilding the relationship, he had the nephews killed and cooked into a feast, which he presented to Thyestes for dinner. He revealed the fate of the boys after Thyestes had eaten.