For years, the rumor existed that Adolf Hitler's paternal grandfather was Jewish, but the claim went unsubstantiated. Now, a new study suggests that the grandfather of the Nazi leader was indeed Jewish.

Published in the Journal of European Studies, the study, authored by family physician and psychologist Dr. Leonard Sax, refutes claims made by the German historian, Nikolaus von Preradovich, who said: "'Not a single Jew’ (kein einziger Jude) was living in Graz prior to 1856."

"Drawing on evidence from Austrian archives from the 1800s, Dr. Sax documents that there was in fact a settled community of Jews living in Graz before 1850," a press release accompanying the study states. "And, Dr. Sax presents overwhelming evidence that Preradovich was a Nazi sympathizer who was offended by the suggestion that Adolf Hitler was a Vierteljude (a one-quarter Jew)."

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"No independent scholarship has confirmed Preradovich’s conjecture," the study's abstract adds.

The claim that Hitler had Jewish ancestry was first put forth by his personal lawyer, Hans Frank. In 1930, 16 years prior to his execution at the International Military Tribunal at Nuremberg, Frank claimed to have uncovered evidence that Hitler's paternal grandfather was a Jewish man living in Graz, Austria.

Frank's claims were eventually published in 1953, as part of his memoirs, after he had been executed for committing war crimes.

According to The Sun, Frank uncovered evidence that Hitler's grandfather lived in the same house where Hitler's grandmother, Maria Anna Schicklgruber, lived.

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Little is known about Schicklgruber until she turned 42. She eventually gave birth to her son, Alois Hitler in 1837, and refused to divulge the details of his father. The priest eventually baptized him Alois Schicklgruber and entered "illegitimate" on the baptismal register.

Schicklgruber later married Johann Georg Hiedler and her last name was changed to Hitler from Schicklgruber, according to the book "The Making of Adolf Hitler." It is unclear why her name was changed to Hitler and not Hiedler. She died in 1847 in Lower Austria.

Rumors first came to light that Hitler had Jewish ancestry while the Nazi leader was still in power in the 1930s. He ordered the SS to investigate the claims and they supposedly found no evidence of any Jewish links.

In 1937, Hitler ordered genealogist Rudolf Koppensteiner to publish a family tree that showed all of his ancestors to be Austrian Germans, The Sun added.

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