Jews are a race of SOULS, and can occupy any physical body they want. The Torah says that Jews ALONE come from God, that makes them a unique race in their own 'twisted' view.
If you check out the excellent article by David Duke (though I know he is still a Christian, very sadly), ALL Jews are real Jews, there were no 'converts' to Judaism that became the Khazar Ashkenazim, they were ALL diaspora Jews in the first place.
If you research properly into the Torah, and forget the widespread garbage about fake Jews, and 'convert' Jews you will come across the real truth, the Jews NEVER EVER allow a single Gentile soul to convert to Judaism. ALL 'converts' are Jewish souls in the beginning, who have merely occupied Gentile positions as crypto-Jews for various reasons such as this:
https://cintayati.wordpress.com/2014/06/09/1492-letter-from-grand-sanhedrin/et's Get This Right: Jews Aren't White!