Leonidas I
According to one version (Herodotus's "Histories", 5.4), Gorgo's grandfather Anaxandridas II was long married without children and was advised to remarry (i.e. take a second wife) which he did. His second wife gave birth to the future Cleomenes I who was thus his eldest son; however, his first wife also became pregnant, and eventually had three sons, including Leonidas I, Gorgo's future husband. Other versions imply that Cleomenes was either born by the king's first marriage or by a non-marital alliance. Most historians favor Herodotus because he is the earliest source. In either case, there appears to have been some tension between the eldest son and his half-brothers. This tension was only resolved by Cleomenes' death, supposedly through suicide or murder, and the accession of Leonidas I (Cleomenes' half-brother and son-in-law).