Atreus
Atreus and Thyestes were the sons of Pelops and Hippodameia. Hippodameia seems to have fitted in well with her in-laws, as she induced her sons to murder Chrysippus, their half-brother -- probably the last cooperative action they engaged in. As a result of that murder, the two were driven into exile in Mycenae.
In Mycenae, Atreus and Thyestes became rulers while the rightful king was away, and when he died, they became kings. They immediately disputed the throne, and in the end, Atreus was king and Thyestes was banished.
Atreus had a son named Pleisthenes who had been brought up by Thyestes. Thyestes ordered Pleisthenes to kill Atreus, and apparently neither Pleisthenes nor Atreus knew their actual relationship, for Pleisthenes attempted the murder and Atreus killed him in self-defense.
Atreus took a gruesome revenge for Thyestes' actions, both in sending Pleisthenes to his death and in seducing Atreus' wife. Atreus pretended to desire reconciliation with his brother and invited him and his whole family to a feast. Thyestes foolishly brought his young sons, who were killed and served up as stew according to the traditional family recipe. Thyestes fled in horror to plot his revenge.
Atreus had two sons, Agamemnon and Menelaus, and also raised the son of Thyestes, Aegisthus, being unaware of their relationship. Atreus sent Aegisthus to kill Thyestes, as Thyestes had sent Pleisthenes to kill Atreus, but Thyestes recognized his son and convinced him to go back and kill Atreus instead. Aegisthus succeeded where Pleisthenes had failed.