Thyestes killed Atreus. While Thyestes ruled Mycenae, the sons of Atreus, Agamemnon and Menelaus, were exiled to Sparta. There, King Tyndareus accepted them as the royalty that they were. Shortly after, he helped the brothers return to Mycenae to overthrow Thyestes, forcing him to live in Cytheria, where he died. As a token of good will and allegiance, King Tyndareus offered his daughters to Agamemnon and Menelaus as wives, Clytemnestra and Helen respectively. When Agamemnon left Mycenae for the Trojan War, Aegisthus seduced Agamemnon's wife, Clytemnestra, and the couple plotted to kill her husband upon his return. They succeeded, killing Agamemnon
Gorgo, Queen of Sparta one son by Leonidas I, Pleistarchus, co-King of Sparta from 480 BC to his death in 458 BC. Her son was a minor at his father's death, so his uncle Cleombrotus (died 480 BC) and then his first cousin and heir Pausanias (r. 480-479 BC) acted as his regent. It was Pausanias who was the architect of the combined Greek victory at the Battle of Plataea (479 BC). After Pausanias fell into disfavor and was accused of plotting treason, Leonidas's son Pleistarchus ruled with the other king of Sparta, Leotychidas II (and then his grandson Archidamus) until his death 459/458