Friends who have not read this history in its entirety are easily biased by some statements. First of all, the result: Yang Jian's original name was Yang Jian, and Li Shimin's real name was Li Shimin; as for Puliuru and Daye, they were all humble surnames given to the heroes by Yuwen Tai, the founder of the Northern Zhou Dynasty. To sort out the causes and consequences of this matter, let's first talk about the entanglement of xianbei surnames and Han surnames during the Southern and Northern Dynasties. Since the fall of the Western Jin Dynasty and the eastern Jin Dynasty, the north has entered an era of chaos with high military force, known in history as the "Wuhu Chaohua". During this period, the Xiongnu, Xiongnu, Xianbei, Qiang, Xianbei and other ethnic minorities who were originally attached to the Western Jin Dynasty entered the Central Plains to establish political power, and the last laugh was the Xianbei Tuoba clan. In 439, emperor Tuoba Tao of the Taiwu Emperor unified the north and temporarily ended the melee; previously, Liu Yu in the south replaced Sima Shi and established Liu Song. In this way, the two major regimes of the south and the north confronted each other, and the history is called the era of the Southern and Northern Dynasties.
After the Yongjia Rebellion of the Western Jin Dynasty, the Xianbei people, who had lived in Daxing'anling for generations, took the opportunity to begin to move south to the Yellow River Valley, including the famous Murong Bu, Yuwen Bu, Tuoba Bu, Tuguhun and so on. And they also established their own political power successively, such as Murong's Yan state, Tuoba's Northern Wei, and so on. Here, we focus on the Northern Wei Dynasty. Their Sinicization is the most successful. Northern Wei unified the north during the reign of Emperor Taiwu Tuoba Tao and became the hegemon of the Central Plains. After Emperor Xiaowen ascended the throne, he moved the capital from Pingcheng to Luoyang in order to carry out his sinicization reform policy. The important part of the reform is to change the Han surname! After Emperor Xiaowen moved the capital to Luoyang, out of the need to intermarry with the Han people and live in a mixed way, he called for the change of xianbei's compound surname to a single surname, and he himself first led by example, changing "Tuoba Hong" to "Yuan Hong".
When The Northern Zhou Emperor Yuwen Tai quelled the rebellion, there was a general named Li Hu who had been loyally following him, and after the counter-rebellion, Yuwen Tai gave the surname of Yang Family, giving this Li Hu the surname of Dayo. And this Li Hu is the grandfather of Li Shimin's father, Tang Gaozu Li Yuan. So since the Li family was given the Ōno clan, when did they change back to the surname "Li"? The Old Book of Tang records this: "Until Emperor Wen of Sui made a portrait, he also reproduced his surname." From this point of view, Li Shimin, who was born in the Sui Dynasty, could no longer be called Ohno Shimin, because the Li family had already restored the Li surname before he was born.
The difference is that some people change their surnames because they take it for granted to be the surname of their subjects, while some people don't want to mention it because they have become ordinary people.