He was born the oldest son of Nobuyasu OKUMA, a feudal retainer of the Saga clan, and Miiko, in the Saga castle town Kaisho-koji alley (current Mizugae, Saga City).
佐賀城下会所小路（現：佐賀市水ヶ江）に、佐賀藩士の大隈信保・三井子夫妻の長男として生まれる。