Are the ancestors of South Koreans and Koreans Chinese?

Yes.

The ancestors of modern Koreans (Korean people) are the Samhan tribe in the south of the peninsula. Goguryeo, which was at the same time as Baekje and Silla, was a country established by the Goguryeo people of the mainland. The name of Goguryeo came from the Goguryeo County under the jurisdiction of the Han Dynasty. At that time, the northern part of the peninsula was the territory of the Han Dynasty, and Goguryeo was a vassal state of the Han Dynasty.

The territory of Goguryeo only took over the territory of the Western Jin Dynasty in the northern part of the peninsula after the Western Jin Dynasty, and has since become the master of the northern part of the peninsula; at this time, Goguryeo has entered the later stage of the dynasty. In the end, Goguryeo was destroyed by the Tang Dynasty, and the northern territory of the peninsula was taken over by the Tang Dynasty. Of course, the Sui Dynasty conquered Goguryeo three times, but failed. The northern part of the peninsula has always been the territory of mainland peoples.

Whether they are people from the Shang Dynasty, the Yan State, the Qin Dynasty, the Han Dynasty, the Western Jin Dynasty, the Goguryeo people, the Tang Dynasty people, the Bohai people, and the Khitan people are all mainland ethnic groups, and they all once owned the northern territory of the peninsula, up and down. There are more than 2000 years. The Koreans (Korean people) really only took possession of the northern territory of the peninsula after the Khitan, that is, after the Goryeo Kingdom established by Wang Jian. ?

Extended information:

The Korea in Chinese history books refers to the Korean state founded by Zhizi from the Shang Dynasty. Later, Weiman from the Yan State replaced the descendants of Zhizi and established Weiman Korea. country. The Koreans (North Koreans) had never established a country named Joseon before the Lee Dynasty's Joseon in the 14th century. However, Chinese history books have recorded the Korean state established by mainland ethnic groups before the Lee Dynasty's Korea in the 14th century.

In 1392 AD, Li Chenggui, the minister of the Wang family in Goryeo, deposed the king and established himself. In 1393, he petitioned the Ming Dynasty with the titles of "Joseon, Hening and other countries" and granted Li Chenggui the title of King of Joseon. The Goryeo Dynasty was renamed Joseon, and academic circles generally call it Lee's Joseon or simply Lee Dynasty. This is how the three Han people became North Korea! .