刘武周
Meanwhile, an intense rivalry had developed between Li Jiancheng, who as the oldest son was Emperor Gaozu's crown prince, and Li Shimin, as Li Jiancheng, while a capable general himself, was overshadowed by Li Shimin, who had done much to solidify Tang rule by destroying Liu Wuzhou, Wang Shichong, Dou Jiande, and Xue Rengao. Li Yuanji supported Li Jiancheng in this rivalry, as he believed that if Li Jiancheng became emperor, Li Jiancheng would create him crown prince. Since their mother Duchess Dou had died in 614, the fact that Li Jiancheng and Li Yuanji had better relations with Emperor Gaozu's favored young concubines than Li Shimin did take a notable importance, since those concubines helped rehabilitate Li Jiancheng's standing before Emperor Gaozu, causing him to no longer consider making Li Shimin crown prince instead, as he considered at one point.