The title of our "King Side by Side" is more from the film and television drama "Legend of Xue". In film and television dramas, Xue was named "King Side by Side" for his great achievements, but the history is really different. Due to the fabrication in film and television dramas, we thought that there was a parallel king in the Tang Dynasty, but in fact, there was no parallel king in Xue's title position in history, and even Xue was not crowned king all his life. Imagine how Xue, who has never been a king for a lifetime, became a king side by side, so there is no such word as king side by side in history.
Then the emperor's highest reward for heroes is to seal the king, but this kind of seal is different from the word "side by side king" and has the same status as the emperor, but the ordinary seal is still lower than the emperor. In ancient times, people who could be crowned king had great achievements, such as Han Xin. But the first king in Han Xin was forced by the King of Qi himself, and the second king of Chu was founded by Liu Bang for fear that Han Xin would appease Han Xin. The appellation of two barons proves Han Xin's achievement and Liu Bang's awe of Han Xin. A baronet with a lower status than himself will be feared by the emperor, not to mention the word "king side by side" with the same status as the emperor. Therefore, the title of "king side by side" will never appear in ancient times.
The emergence of the title of "King Side by Side" may be more about people's praise of heroes at that time, and gradually produced a title that only unofficial history had.