Why do some people say that Jews are descendants of Judah?

Israel has twelve sons, namely Reuben, Levi, Simeon, Judah, Gad, Issachar, Zebulun, Yue Se, Benjamin, Dan, Asher and Naphtali, of which Judah is the fourth son.

After Israel 12 branches were sent to Egypt, the United Kingdom of Israel was established in BC 1030. By 950 BC, the State of Israel was divided into the Kingdom of Judah in the south and the State of Israel in the north. In the later history, people from Israel 10 tribes intermarried with foreigners and disappeared, while the rest of Judah kept their religion and lineage. Is the ancestor of modern Jews.

King David is the second most important man in Israel and a descendant of the tribe of Judah. Many people in Israel are called Judas, including Judas who betrayed Jesus, and Jesus' brother is also called Judas.