I have read that only 10% to 15% of people who are considered to be Jews today are in anyway connected to those who lived in Judea at the time of Christ. If that is factual then there are probably many other reasons that there are so many diverse opinions on who’s who and what it all means.
When a people starts being called by a “nickname” it tends to stick - sorta like “Yanks” or “Brits”. It doesn’t denote any kind of genetic tie. Judaism does now and has always accepted converts. Converts would not necessarily be genetically related to any particular tribe.
When a person converts to Judaism, they become Jewish in every sense of the word. When a woman converts to Judaism and later has children - those children are Jewish by birth. And the family line is accepted to be Jewish thereafter unless one of them converts to another religion.
The idea that bloodline is the be-all, end-all in Jewish life is a misinterpretation of our texts usually misinterpreted by Christians. I understand that there is a Christian end-time prophecy regarding the 144,000. I understand the Christian hunt for the “Lost Tribes”, I understand the reason behind that hunt and I understand the reasoning behind Christian attempts to convert Jews to Christianity. I also understand the prophecies regarding the Antichrist, the 7 year period, the slaughter of the Jews, the third temple and so on.
But in order for you to understand what I am talking about - you need to understand this about Jews: There is nothing other that G-d. Nothing exists that G-d did not create. There is no place of origination, no place of destination other than G-d. Observant Jews believe that we all stood together in spirit at Sinai - Every Jew who would ever be born was there and that includes those who would convert to Judaism.
If you have questions about the validity of this teaching, please take note of the brilliance of G-d: Christians who believe that bloodlines are so very important - Jesus was from the “line of David” - David, the King of Israel. David, beloved of G-d. David, the murderer, the adulterer. David, slayer of giants and singer of songs. David, the beautiful grandson of a convert.