For Ieyasu, Iemasa was not only a grandchild from a daughter married into another family, but also the eldest grandson (he was older than his uncle Hidetada), so Ieyasu treated Iemasa preferentially and gave him swords and hawks.
家康の外孫に当たる上に家康にとっても最年長の男孫であった事（叔父・秀忠よりも年長）から、刀や鷹を与えられるなど、重用された。