Yoshikaze was the oldest son of Prince Shigeyo in Gyobusho (Ministry of Justice) of Kaga province, who was a son of Imperial Prince Nakano, who was a son of Emperor Kammu, and Yoshikaze demoted from the Imperial family to a subject in 874 and called himself one of the Taira clan.
桓武天皇の子・仲野親王の子・刑部省加賀国茂世王の長子であり、貞観(日本)16年（874年）に臣籍降下して平氏を名乗るようになった。