Lifespan: Tenshō 18 (1590) to 5/6 of Keichō 20 (1615)
Other Names: Kumamaru, Chōjirō
Lord: Tokugawa Hidetada
Father: Yamaguchi Shigemasa
Mother: Daughter of Ozaka Katsuyoshi
Siblings: Shigenobu, Shigenaga, Hirotaka, Shigetsune
Wife: [Formal] Daughter of Ishikawa Yasumichi (or Ishikawa Tadayoshi)
Yamaguchi Shigenobu served as a bushō during the Azuchi-Momoyama and early Edo periods.
In 1590, Shigenobu was born as the eldest son of Yamaguchi Shigemasa in Kiyosu in Owari Province. Shigemasa was a daimyō and the lord of Hoshizaki Castle in Owari, serving as a retainer of the Oda clan.
In 1597, Shigenobu met in person with Tokugawa Hidetada. On 12/27 of Keichō 14 (1609), Shigenobu was conferred with the title of Junior Fifth Rank (Lower) and Governor of Izu. Thereafter, he received as his formal wife the adopted daughter of Ōkubo Tadachika, but the marriage arrangements had not received the official approval of the bakufu so, on 1/6 of Keichō 18 (1613), his father, Shigemasa, was removed from his position as a daimyō and, together with his father, Shigenobu was ordered confined to the Ryūon Temple in the Koshio manor in the Iruma District of Musashi Province.
In 1614, at the time of the Winter Campaign of the Siege of Ōsaka, Shigenobu and Shigemasa headed toward Ōsaka with the intention of making contributions on the battlefield, but, after being stopped at a checkpoint in Hakone, temporarily returned to the Ryūon Temple. Thereafter, in a plan to get through the checkpoint, they disguised themselves as merchants and made their way to Ōsaka via the Tōsan Road, but a settlement had already been reached so they returned again to the Ryūon Temple.
The next year, at the Summer Campaign of the Siege of Ōsaka, Shigenobu joined the army of Ii Naotaka and fought valiantly, but, during the Battle of Yao and Wakae, was struck down by a retainer of the Toyotomi named Kimura Shigenari. He was twenty-six years old.