Actually, the fifteenth Shogun Yoshinobu TOKUGAWA was a son of Nariaki TOKUGAWA, the ninth lord of Mito Domain, so the last Shogun of the Edu shogunate was in truth from the Mito family; however, he had been adopted to the Hitotsubashi Tokugawa family, and therefore formally he was from the Hitotsubashi Tokugawa family, that is to say, this was not exactly the case that a Shogun was selected from the Mito family.
なお、一橋徳川家の養子に入っていた九代藩主徳川斉昭の子徳川慶喜が十五代将軍となることによって江戸幕府最後の将軍を出すこととなったが、あくまで一橋家から将軍を出したのであって水戸家から将軍を出したわけではない。