 The problem lies in that the heir designated by Darius I is Xerxes, not Masistes, although the succession was not free of conflict.According to Herodotus, the eldest son by Darius was Artabazanes, but he had been born prior to Darius' ascent to the throne.Xerxes was the first-born son of Darius after he was crowned king, and he was also son of Atossa, the daughter of Cyrus the Great, founder of the empire.