Nanbu clan
Nobunao was the second son of Nanbu Masayasu, the 22nd chieftain of the Nanbu clan, and was born at the clan’s Ikatai Castle in what is now the town of Iwate in 1546. In 1565, he was adopted by his cousin, the 24th chieftain of the Nanbu clan Nanbu Harumasa to be his heir, and resided at Sannohe Castle. In 1566 and 1568 he successfully defended the clan’s territory in Kazuno against incursions by the forces of Andō Chikasue.