Argos came into the power of Agamemnon, who had married Clytemnestra, the sister of Castor and Pollux, while his brother Menelaus married the beautiful Helen.  All the Greek heroes had been suitors for Helen, the fairest woman living, and they all swore to one another that, choose she whom she might, they would all stand by him, and punish anyone who might try to steal her from him.  Her choice fell on Menelaus, and soon after her wedding her brother Castor was slain, and though Pollux was immortal, he could not bear to live without his brother, and prayed to share his death; upon which Jupiter made them both stars, the bright ones called Gemini, or the Twins, and Menelaus reigned with Helen at Sparta, as Agamemnon did at Mycenæ.