Actually, Karl had 4 Jewish grandparents. So I think he would have been in trouble under Nuremberg.
I think it is interesting that the Nuremberg Laws were not nearly as severe against Mischlings as most people assume. A far cry from the “one drop rule,” anyway.
Actually, I understand his father’s mother was not Jewish, which is why he was basically kicked out of the Marx family and was unable to train as a Rabbi.
She had attempted to convert, but Marx (the dad) was a Cohen (their actual name was “Levi”) and thus not eligible to marry a convert, so he left Judaism altogether. It had nothing to do with employment.
Marx’s mom was of some sort of mixed heritage; I would have to ask my wife -— she is actually kin to this crew (along with Adm. Hyman Rickover, which is ironic as heck), which is the only reason I know this.