Emperor Kōkaku
Chikamune was the eldest son of Date Narimura. His childhood name was Masachiyo (政千代). His mother, Nobuko, was the daughter of the "kampaku" Takatsukasa Sukehira, thus making Chikamune the second cousin of Emperor Kōkaku. His mother died shortly after his birth due to complications with the pregnancy, and both his grandfather and father followed during the same year, leaving the infant Chikamune as "daimyō" of Sendai. Normally, this would be cause for the Tokugawa shogunate to appoint a "metsuke" to oversee the domain until his majority, or could even be a cause of attainder, so the domain's officials kept the fact of Date Narimura's death a secret for several months until the succession was confirmed. In the same year, the infant Chikamune was wed to Aya-hime, a daughter of "Shōgun" Tokugawa Ienari. During this period, his grandmother, Kanshin-in, wielded great influence.