Due to the huge contradiction between Tang Gaozu and Li Shimin, Li Shimin initiated the change of Xuanwu Gate. Tang Gaozu knew that his sons were killing each other, but he still had a lot of complaints about Li Shimin. So before he died, Tang Gaozu said to Li Shimin, "If you kill my child, your child will die." Such malicious words, Li Shimin ignored, but finally came true.

Tang Gaozu, the meaning of this sentence is obvious, that is to say, you killed my descendants, and your descendants will follow your example and kill your descendants in the future. Because of the Xuanwumen rebellion, he killed his other two sons and Li Yuanji. Therefore, Tang Gaozu cursed Li Shimin, saying that his descendants would kill each other like him.

Although Li Shimin was a very powerful emperor, the Tang Dynasty reached a peak of prosperity when he was in power, but the way he gained the throne was also a black history in his life. He initiated the Xuanwumen Rebellion, killed Li, the Prince of the East Palace, and killed Li Yuanji, then forced his father Li Yuan to abdicate and became emperor himself, calling him Emperor Taizong.

This incident is a great blow to Tang Gaozu. Plus, he was old and in poor health, so he fell ill. Later, before he died, he said such cruel things to Li Shimin. Shortly after Tang Gaozu's death, this sentence really came true. Li Shimin's eldest son, Li Chenggan, became the Crown Prince in 15, and was later abolished due to rebellion. He died in exile at the age of 25. Li Shimin's second son, Li Kuan, also died young and had no offspring. In the end, several children in Li Shimin died young because of killing each other or being murdered.