Du Ruhui
In 626, Li Shimin seized power after ambushing and killing his older brother Li Jiancheng, the Crown Prince, and younger brother Li Yuanji, the Prince of Qi, at the Incident at Xuanwu Gate, and later that year, Emperor Gaozu yielded the throne to him (as Emperor Taizong). Emperor Taizong created Li Chengqian's mother Princess Zhangsun empress, and created Li Chengqian crown prince. In 630, in order to show honor to the chancellor Du Ruhui in Du's illness, Emperor Taizong sent Li Chengqian to personally visit Du. Later that year, Emperor Taizong formally made Li Chengqian in charge of listening to legal appeals where the litigants were dissatisfied with the judgments made by the executive bureau of the government (尚書省, "Shangshu Sheng"), putting a layer of appeal between the executive bureau and the emperor himself. The senior officials Li Gang (李綱) and Xiao Yu were made his senior advisors, and whenever Li Chengqian were officially hearing governmental matters, he would be accompanied by Li Gang and the chancellor Fang Xuanling. In 631, he held his official rite of passage. In winter 632, after a feast Emperor Taizong held for Emperor Gaozu (then with the title "Taishang Huang" (retired emperor)) at Emperor Gaozu's Da'an Palace (大安宮), Emperor Taizong wanted to hold up Emperor Gaozu's litter personally; Emperor Gaozu disallowed it, but had Li Chengqian take Emperor Taizong's place in doing so. Meanwhile, by 633, Li Chengqian was said to be beginning to favor frivolous games, and his staff members Yu Zhining, Du Zhenglun, and Kong Yingda often advised him to not do so. Emperor Taizong approved of Yu, Du, and Kong, and rewarded them.