As far as being descendants of the Israelites... when someone " finds out their ancestors were Jewish", the only thing they have found out is they had ancestors in a cult claiming to be descendants of the Israelites when they had NO possible evidence.. They might be Lemmings by heritage, but they are not Jewish by heritage.
How many nazi Jews... The author writing the book on Jews in the nazi army, found out his mother was a descendant of these calling themselves Jews... ONLY AFTER RESEARCHING SOME FAMILY HISTORY.
When people become important, note how the Blight cult adds them to their famous Jews list. Madam not-so-bright, Evils, Einstein. ( of course Einstein was an atheist so if he was right there could be no such thing as a Jew )
It is like becoming a member in the Mormon church, once you are in, they find links to your ancestors you never had any idea of.
In this guy's book he found about 150,000 "Jews" in the nazi army.
* No one was doing any family tree search
* Those Germans who had any knowledge of the false Jew cult members of their family trees kept their shame concealed.