 She was the daughter and the only known child of Cleomenes I, King of Sparta (r. 520–490 BC) during the 6th and 5th centuries BC.She was the wife of King Leonidas I, Cleomenes' half-brother, who fought and died in the Battle of Thermopylae.Gorgo was also the mother of King Pleistarchus, her only son with co-King Leonidas I.