He was the first son of
Sanada Masayuki and his wife, Kansho-in. His younger brother was
Sanada Yukimura. He was married to
Komatsuhime (Inahime),
Honda Tadakatsu's daughter and adopted daughter of
Tokugawa Ieyasu. Two other wives of Nobuyuki were his first wife and cousin Seiin-in, who lost her status to Komatsuhime and Ukyo (a daughter of Tamagawa Hidemasa). At an early age, Nobuyuki's father served under the
daimyō Takeda Shingen and his son
Takeda Katsuyori and sent Nobuyuki as a hostage to prove the Sanada clan's loyalty to the
Takeda clan. After the Takeda clan was destroyed by
Oda and
Tokugawa army, Nobuyuki fled to
Ueda Castle, the stronghold of the Sanada Clan and where his family were. In 1582, Later, Nobuyuki participated in the
Tenshō-Jingo war. At first, Nobuyuki and his father aided with the Hojo clan. However, at the urging of Yoda Nobutada, a Takeda retainer who had loyally served Tokugawa Ieyasu , and his uncle, Sanada Nobutada, Nobuyuki recaptured Numata Castle from the Hojo forces. In 1585,
Tokugawa Ieyasu attacked
Ueda Castle; Nobuyuki fought in Battle of Kami river alongside his father and was victorious. Later, as Masayuki served under Toyotomi Hideyoshi, Nobuyuki was sent to Tokugawa to be a retainer in order to preserve the clan if anything wrong happened to the Toyotomi clan. ==Battle of Sekigahara==