Although he was a second son, his eldest brother, Kamemaru HIRANO, died young, therefore, Nagahiro succeeded as the head of a family and became hatamoto (direct retainers of the bakufu, which is a form of Japanese feudal government headed by a shogun) with fief of 5,000 koku (crop yields).
次男だったが、長兄の平野亀丸が早世したため、後を継いで5000石の旗本となる。