i don't think anyone will know for sure.
One theory is Maria Schikelgruber,the mother of Alois Hitler worked for a jewish family and became pregnant by a son of the family.True or not I don't know.
I don't know how much digging around anyone has done into maria Schikelgruber.Her family history,and all the places and people she worked for.This might help to either give some credience to the rumors or not.
I also think IF IT COULD BE DONE,exhum Alois Hitler father of Adolf,and run DNA tests on him with I believe George or Johann Hitler who supossedly fathered him. When Maria married one of the Hitler brothers,George I believe never adopted him. Alois also changed his name to Hitler.There are several books on this subject.
Rumor also has it that Hans Frank,a high ranking Nazi party member was asked by Hitler
to go to Austria and do some digging around in the family tree.Supposedly he found the Austrian Government had some ino on Hitler's so called Jewish blood. I believe Frank mentioned this to the folks at Nuremberg,but he is the only source.
The nazis due to Hitler were obsessed with this deal.
i remember my dad talking about his second cousin,Rheinhold von Lillienschild. He was an artillary officer in WW1 and a mechincal engineer and metalurgist.
Someone accused him of being a Jew and the Gestapo did a genealogy check.His family fought in the Crusades and go back in the records of the City of Riga,latvia to the 13th or 14th century.he had no Jewish blood.
A friend tipped him off to the fact the Gestapo
was coming to arrest him.He made it on the boat to America just ahead of them.He was not a fan of Adolf's and probably made no secret of it.
I know my father's family in Bavaria have a family history book which is kept by relatives in Nuremberg.One of the relatives in Garmisch in the 1690s was a steward to the king,and the family consists of artisans,land holders,petty court officals and military men.The toy makers Andreas and Johann Georg Hilpert are 16th cousins.They were the first to mass produce toy soldiers known as flats.Their works can be found in books and museum collections.
It really makes you wonder if Hitler had not believed he possibly had jewish blood,would there have been a Holocaust. Not just of jews,but slaves, gypsies and others.
Also,don't forget Hitler was born in the Austro -Hungarian Empire,not Germany.
So you have Hungarians,Serbs,Slavs,Croatians,Polies and other groups who either were born in the place or immegrated to Austria.
maybe that was why Hitler also tried to kill Slavs,Russians ,Poles and others.
maybe not a Jew,but maybe a Hungarian or Gypsy froliced with old Maria if you get my drift.