Wang Chengzong
Wang Yuankui was born in 812, during the reign of Emperor Xianzong, when his father Wang Tingcou was probably serving as an officer under Wang Chengzong, then the military governor of Chengde, whose family Wang Tingcou was related to by adoption — as Wang Tingcou's great-grandfather Wang Wugezhi () was an adoptive son of Wang Chengzong's grandfather Wang Wujun. After Wang Chengzong's death in 820, the imperial government briefly took over control of Chengde, but in 821, soldiers led by Wang Tingcou mutinied and killed the imperially-commissioned military governor Tian Hongzheng, and Wang Tingcou subsequently took over as military governor, with the imperial government eventually capitulating and allowing him to do so.