The question arises, what of the descendants of the so-called "lost tribes"? Are they still considered like Jews or are they on the level of the gentiles?
Keep in mind that this is purely my own reasoning based on my own learning of the sources, but my answer is that they are on the level of gentiles, if they were born into gentile bodies, until they are re-born as Jews through conversion. However, some are born as Jews and simply have no knowledge of their tribal identity. (Spiritual rebirth through conversion was originally a Jewish concept co-opted by the xians.)
First of all it needs to be understood that a number of Israelites from the Northern Kingdom made their way to Judea before the exile to Babylon, but without their tribal land, over time they lost their tribal identity.
We see from the account in the book of Ezra (2:59-62) that in the wake of the Babylonian exile and subsequent return to Eretz Yisrael there were those who could not prove their lineage...
These are the ones who went up from Tel-melah, Tel-harsha, Cherub, Addan and Immer, and could not declare their fathers' families and their descent, whether they were from Israel....
Of the children of the Kohanim: The children of Habaiah, the children of Hakkoz and the children of Barzillai, who took wives from the daughters of Barzillai of Gilead and were called by their name. These sought their genealogical records, but they could not be found, so they were disqualified from the priesthood.Some sources suggest that one of the jobs of Eliyahu the Prophet in the future will be to reveal to each person his tribal affiliation. It's not something anyone today can prove. It's not a matter of physical DNA, but spiritual DNA.
We saw from the writings of the Ramchal with regard to Yishmael and Eisav, that while both of them were physical descendants of Avraham, yet his spiritual legacy was only inherited through Yitzchak and Yaaqov, these other two being deemed "unworthy".
Anyone today unable to show an uninterrupted tradition of family Jewish identity - not unlike the Ethiopian, Bnei Menashe and Anusim communities - are "disqualified" like those described in the book of Ezra. And like these other communities, they will return by means of the law itself - by formal conversion.
So, that's one way the "lost" tribes could regain their Jewish identity until Eliyahu comes and clarifies their tribal affiliation. Another way is through simply being born a Jew. There was a rabbi in Eretz Yisrael about seventy years ago who said that the tribes were all represented in the modern return to Eretz Yisrael and that the Jewish people tended to unwittingly choose to settle within their own tribal portion, i.e. they are attracted to those regions without any conscious awareness of it.
On the other hand, we know that some with a demonstrable Jewish lineage are Erev Rav without Jewish souls. And we have many modern rabbis who teach that this generation of Jews is made up in part of the reincarnated souls of the 600,000 who left Egypt - which would include those from every tribe.
What actually distinguishes a Jew from a non-Jew is an additional level of soul. We are told that Jews receive an additional level of soul on Shabbat that leaves us when Shabbat goes out. And we are told that a Jew who makes aliyah receives an additional level of soul when he enters Eretz Yisrael and that it remains behind when he leaves the land. A convert receives his additional soul that makes him into a Jew when he comes up out of the mikvah.
In short, we are talking about a spiritual dimension of humanity that the Creator Himself oversees and He alone knows for sure who has what kind of soul and at what level.
He gave into the rabbis hands the knowledge of the process of creating Jews from non-Jews and only when those intructions are followed to the letter will the appropriate soul level be attained. As to its tribal identity, the Creator has not seen fit to make that knowledge known at this time, but He knows and He promised that all would return.
And at the end, all those who were "disqualified", for whatever reason, or did not truly have Jewish souls, like the Erev Rav, will be purged from Am Yisrael by HKB"H.
So, in case I've muddied the waters more than I've clarified them, allow me to reiterate: according to all the sources I know, with the exception of the Erev Rav, only Jews are on the level of "children" while non-Jews are HKB"H's "creation", including those who may once have been identified as Israel in a previous lifetime.
Again, this is my personal informed opinion. Hope that helps.