Tribes have pretty freely intermarried for 2,500 years or so, that’s for sure.
...While many have the idea that all Jews now are descendants of only two and a half tribes, the truth is that when the ten tribes were captured and sent into exile, a tenth of their population remained. As the prophet Amos proclaims, “For so said the Lordd: The city that gives forth a thousand shall remain with a hundred, and the one that gives forth a hundred shall remain with ten, of the house of Israel.”
...Jeremiah was on a divine mission to the ten tribes, and in fact he actually gathered them up and returned them to Israel, where Josiah ruled over them.
This, however, does not mean that the prophet Jeremiah returned all of the exiles. Rather, he gathered only some people of the ten tribes who had managed to escape while being led into exile. They then joined the rest of the Jewish nation and are included in their history...
Thanks for the link, jjotto. Very interesting.