Where do the descendants of the ancient Israelites live today, in this 21st. century?

Well, first of all, you must understand that, for the most part, they are not the people called Jews living in that little country in the middle east we call Israel today.

Oh, some of the residents of that little country are indeed J
udahaits and
 Bejaminites, i.e. the Good Figs. (from the ancient Israelite tribes of Judah and Benjamin) but the majority, refereed to in the Bible as strangers, are descendants of Caini.e. the Bad Figs, who started mixing with the Israelites back in the days when David was king of Israel and continued to mix with the remnant of the House of Judah, who had not been a part of the Assyrian invasions in 745 - 721 B.C., and were still living in and around Jerusalem when Jerusalem was taken by king Nebuchadnezzar of Babylon in 586 B.C., way back before Christ's first advent, and many more living there today who are of Khazar ancestry, i.e. also Bad Figs who converted to Judaism about 740 A.D.

Relevant studies below:

Live Link to- Jeremiah's vision of both Good And Bad Figs. 

Picture a temple, with two baskets of figs sitting on the steps before the temple. That is the setting.

Jeremiah 24:2 "One basket had very good figs, even like the figs that are first ripe: and the other basket had very naughty figs, which could not be eaten, they were so bad."  Jeremiah 24:3 "Then said the LORD unto me, What seesth thou, Jeremiah? And I said, Figs; the good figs, very good; and the evil, very evil, that cannot be eaten, they are so evil."

Live Link to-  "Pastor, I challenge you to prepare and preach a sermon on two verses of the Bible. "Acts 26: 6-7."

Live Link to-  Only a remnant of the Judahiats were left for Nebuchadnezzar to take to Babylon in 586BC.
Live Link to-  Who are the KHAZARS?
Live Link to-  The Parable of the Fig Tree
 Live Link to- Are you a Israelite? "Do you know who you really are?"