 From 1702, he was named heir and was given the childhood name of Katsumaru (勝丸) later Matsudaira Inuchiyo-maru, later becoming Toshitaka (利挙) and then Toshioki (利興).He underwent the "genpuku" ceremony with "Shōgun" Tokugawa Tsunayoshi presiding and was renamed Yoshiharu (吉治).In 1708, he was wed to Matsuhime, the adopted daughter of Tokugawa Tsunayoshi, the daughter of Tokugawa Tsunanari of Owari Domain.