Empress Kōjun
Prince Hiroyasu was born in Tokyo as Prince Narukata, the eldest son of Prince Fushimi Sadanaru (1858–1923) by one of his concubines. He was the twenty-third head of the Fushimi-no-miya, one of the four "shinnōke" cadet branches of the imperial family entitled to succeed to the throne in default of a direct heir. Prince Fushimi was a second cousin to both Emperor Shōwa (Hirohito) and Empress Kōjun, and nephew of Prince Kan'in Kotohito