Although Iemitsu's father and second Shogun Hidetada had his first son Chomaru in 1601, because Chomaru died young, Iemitsu was treated as the heir and was given the childhood name of "Takechiyo," the same childhood name of his grandfather, Ieyasu TOKUGAWA.
徳川家の世継であった父・秀忠には慶長6年に誕生した長男・長丸がいたが、既に早世していたため世子として扱われ、祖父・徳川家康と同じ幼名竹千代を与えられた。