Toyonao's father Kazusanosuke YAMANA was a kokujin (or ji-samurai, which was a lord of smaller rural domains in feudal Japan) who ruled Asago-gun County of Tajima Province, and Toyonao took over as head of the family, thereby becoming the Lord of Yakuno-jo Castle.
山名氏で但馬国朝来郡の国人であった山名上総介を父とし、家督を継いで夜久野城主となった。