Johann Georg Hiedler (baptised 28 February 1792 – 9 February 1857) was born to Martin Hiedler (17 November 1762 – 10 January 1829) and Anna Maria Göschl (August 23, 1760 – 7 December 1854). He was considered the officially accepted paternal grandfather of Adolf Hitler by the Third Reich. Whether Johann Georg was in fact Hitler's biological paternal grandfather is considered unknown by modern historians, but his case is the most plausible and widely accepted.
He was from Spital, Austria, and made his living as a wandering journeyman miller. He married his first wife in 1824 but she died in childbirth five months later. In 1842, he married Maria Anna Schicklgruber and became the legal stepfather to her illegitimate five year old son, Alois. It was later claimed Johann Georg had fathered Alois prior to his marriage to Maria, although Alois had been declared illegitimate on his birth certificate and baptism papers; the claim that Johann Georg was the true father of Alois was not made after the marriage of Maria and Johann Georg, or, indeed, even during the lifetime of either of them. In 1877, twenty years after the death of Johann Georg and almost thirty years after the death of Maria, Alois was legally declared to have been Johann Georg's son.
Accordingly, Johann Georg Hiedler is one of three people most cited by modern historians as having possibly been the actual paternal grandfather of Adolf Hitler. The other two are Johann Nepomuk Hiedler, the younger brother of Johann Georg, and a Graz Jew by the name of Leopold Frankenberger.
In the 1950s, this third possibility was popular among historians, but modern historians now have debunked the third possibility as the Jews were expelled from Graz in the fifteenth century and were not permitted to return until the 1860s, several decades after Alois was born.