李建成
In 623, when the Eastern Tujue made another incursion into Tang territory, Li Yuan again sent Li Jiancheng and Li Shimin to guard against the attack. Meanwhile Li Yuanji suggested to Li Jiancheng that he could have Li Shimin assassinated when Li Shimin was visiting Li Yuanji's mansion, but Li Jiancheng refused, not having the heart to kill a brother.