Dou Jiande
Yuwen Chengdu is based on Yuwen Chengji (宇文承基), the son of Yuwen Huaji in real history. However, in the real history, Yuwen Chengji would just be a nobody without his father. After the military rebellion, Yuwen Chengji was killed by Dou Jiande (窦建德) along with his father Yuwen Huaji, uncle Yuwen Zhiji (宇文智及), and younger brother Yuwen Chengzhi (宇文承趾),the archetype of Yuwen Chenglong (宇文成龙) in the novel. The only survivor of his family, Yuwen Shiji (宇文士及), eventually became a top officer in Tang Dynasty.