What did the stupid prince of the Tang Dynasty do at the princess's wedding, which made Li Shimin doubt his life?

The monarch said in front of everyone that Princess Honghua was not Li Shimin's own daughter because she was drunk. Because of Li Daoming's words, Li Shimin was very embarrassed.

Since Li Daoxuan had no children at that time, his official position and title were inherited by his younger brother Li Daoming after his death. It can be said that Li Daoming can easily sit on the title of monarch. At that time, Li Daoming was not only a monarch, but also a military commander with the highest power at that time. He can achieve so much because of the influence of his brother Li Daoxuan.

Although Li Daoming had an official position at that time, he did nothing all day and made no special contribution to the court. Because Li Shimin wanted to woo Tuguhun at that time, he asked Li Daoming to contribute his daughter and let her marry Tuguhun Khan. At first, he divided Li Daoming's daughter into Princess Honghua, and claimed that Princess Honghua was his own daughter.

So at that time, Li Daoming's daughter married Tuguhun as a princess. According to custom, a father must attend his daughter's wedding after marriage. So not far from Li Daoming, Wan Li came to Tuguhun to attend her daughter's wedding. As a representative of the princess family, Li Daoming received a grand reception at the wedding. At that time, many officials toasted Li Daoming in succession. As a result, Li Daoming boasted in front of everyone that Princess Honghua was not Li Shimin's own daughter, just because he was drunk at that time, and the atmosphere of the whole wedding became particularly embarrassing. Although Tuyuhun people knew that the emperor would never kiss his daughter, everyone treated it with transparency. It is because of Li Daoming's words that Li Shimin doubts life.