Please Let me restate my questions, does anyone know what Old Testament tribe they have descended from today? I had asked before but I was to gauge about the real question?
I believe that they have done genetic testing on Kohanim. (I have to locate that article, but I recall reading about this about a year ago.)
At any rate, Koahnim and Levi'im are certainly from the tribe of Levi. If someone claims to be either of these, we believe his word. Do we have exact proof, other than above-mentioned DNA testing? No, we don't. But we have a general assumption that if numerous generations within the family have made this claim, it is reliable, though, of course, there have been cases where someone in the family erred. (I know someone who thought he was a Kohen, and eventually discovered that he wasn't.)
As for the rest, I don't believe there is definitive knowledge of which tribe people came from, though most people who are not in the above group claim to be from the tribe of Judah.