刘武周
Yang Yan was born in 727, during the reign of Emperor Xuanzong. His family was from Fengxiang (鳳翔, in modern Baoji, Shaanxi) and claimed ancestry through officials of the Warring States period state Han), Qin Dynasty, Han Dynasty, and Sui Dynasty, although the lineage was not completely traceable. His great-grandfather Yang Dabao () served as a county magistrate during the reign of Tang Dynasty's founder Emperor Gaozu and was killed when resisting a rival contender for the throne, Liu Wuzhou the Dingyang Khan, and therefore was posthumously honored. His grandfather Yang Zhe () was known for his filial piety. His father Yang Bo () was known for having passed the imperial examinations but then declined official offices to support his parents, an act for which he was honored by both Emperor Xuanzong and Emperor Xuanzong's son Emperor Suzong.