Footnote: Someone asked about this, so I thought I should clarify. I wrote:
I am supposed to be of the tribe of Judah and House of David...
The words to note are "I am supposed to be."
I was asked, How do you know this?
Tradition and documentation.
The documentation comes mainly from the records of the Spanish Inquisition and the work of academic historians who have noted that some of my ancestors during their trails and torture claimed to be of the House of David. They raised this point to ask how they as Christians planned to explain to Christ in the afterlife what they did to their own relatives. Some Christian historians have called this a 'sad attempt' by my ancestors to avoid persecution. But these statements have been judged as demonstrative of anti-Semitism on behalf of the historians who felt these Jews were lying.
Tradition comes into play here. According to Obadiah 1:20, the "inhabitants of Jerusalem" had been exiled to a place called "Seferad" or "Sepharad" (there are various spellings). While the exact place is unknown, it is likely that this is mentioning the place where the House of David had been placed by the Babylonians to separate them from them the rest of the exiles. This is merely speculative, for no one knows exactly where this place was.
Perhaps, due to legend, after the Roman diaspora, it seems that most of the Cohen line (Levitical), went north into Ashkenazi territory (which became Poland, Austria, and Germany). These Jews mixed with the people of the Ashkenazi origin. These became the Ashkenazi Jews (and the last four letters of Ashkenazi is where "Nazi" comes from, the Jews mixing with these people the reason Hitler felt the need to "purge" them from the "master race").
Others, traditionally Judean and Benjaminite, went to "Sepharad." All that is clear is that by the 2nd century, the Jews were calling the Iberian peninsula by this name. It later became Spain and Portugal. Was this because the House of David was originally placed here? Was the name merely traditional, lifted from Obadiah? No one knows. Because they shared the Iberian peninsula with Arabs/Muslims, there was little mixing of the two groups allowed. Some Sephardic Jews are believed to have been of the House of David, the great teacher Maimonides among the top of the list (though he never publicly admitted to this). According to records it seems I am related to Maimonides from my mother's mother and her line, but both sides of my family, my paternal line as well, has Sephardi roots.
The only DNA marker that exists, however, is the Cohen one. There is no marker for the Davidic line. There is rabbinical support to the claims of my family, and I did grow up hearing stories from the women in my family that we were descendants of royalty and that if I were to marry they would have to investigate the family (a common tradition that rabbinical authorities claim exist in some Crypto-Jewish families which might be Davidic).
And there you have it. As to what it means, besides learning the history, there is nothing else of value I can say it gives to me. It is not where I come from that matters as much as what I do with my life now. And since there is not much to go on definitively, I can only say according to tradition "I am supposed to be." But I make no claim to the validity of this nor that it makes me any more special than anyone else in the end.