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. This version is however not supported by other sources, which 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, resolved only by the former's death (or murder) and the accession of Leonidas I (at once his half-brother and his son-in-law).