In October, 1842, he was born in Tokiwa-mura, Toichi County, Yamato Province (present-day Tokiwa-cho, Kashihara City, Nara Prefecture), as the eldest son of Koji KAYANO, and later became the heir of the Moriyama family.
天保13年（1842年）9月、大和国十市郡常盤村（現在の奈良県橿原市常盤町）に萱野恒次の長男として生まれ、後に森山家を継いだ。