His father, Tadayoshi TORII, had served the TOKUGAWA clan since the clan called itself the MATSUDAIRA clan and he once worked as Okazaki magistrate and the like; Mototada had served as one of Ieyasu's aides since Ieyasu was Imagawa's hostage and called Takechiyo MATSUDAIRA.
父の鳥居忠吉は岡崎奉行などを務めた松平氏以来の老臣で、元忠も家康がまだ「松平竹千代」と呼ばれて今川氏の人質だった頃からの側近の一人である。