李承乾
In 643, Li Chengqian was discovered to have conspired with his uncle Li Yuanchang () the Prince of Han, his brothers-in-law Zhao Jie () and Du He (), and the general Hou Junji, to overthrow Emperor Taizong (over his fears that Emperor Taizong would replace him with his favored brother Li Tai the Prince of Wei). Emperor Taizong deposed Li Chengqian and replaced him with a younger son, Li Zhi the Prince of Jin. Most of Li Chengqian's staff were blamed for not correcting his behavior and were demoted or exiled, but Yu was praised for having tried to correct Li Chengqian. Emperor Taizong subsequently made him a member of Li Zhi's staff.