Johann Nepomuk was named after a Bohemian Saint Johann von Nepomuk. Some view this name as evidence that Johann Nepomuk and subsequently his great-grandson Adolf Hitler had some Czech blood. However, Johann von Pomuk/Johann Nepomuk, was an important saint for Bohemians of both German and Czech ethnicity. Using Nepomuk just indicates ties to Bohemia and central Europe.
Johann Nepomuk became a relatively prosperous farmer and was married to Eva Maria Decker (1792–1873) who was fifteen years his senior. On 19 January 1830, Eva Hiedler gave birth to Johanna. Legally, he was the step-uncle of Alois Schicklgruber (later Alois Hitler), the stepson of his brother Johann Georg Hiedler, a wandering miller.
For reasons unknown, Johann Nepomuk took in Alois when he was a boy and raised him. It is possible that he was, in fact, Alois' natural father but could not acknowledge this publicly due to his marriage. Another, and perhaps simpler, explanation for this kindness is that Johann Nepomuk took pity on the ten-year-old Alois and took him in. Alois was, after all, the stepson of his brother Johann Georg, and Johann Nepomuk may have known that in fact Alois was Johann Georg's natural child. After the death of Alois' mother Maria, it could hardly have been a suitable life for a ten-year old child to be raised by an itinerant miller.
In any case, Johann Nepomuk left Alois a considerable portion of his life savings. Johann Nepomuk's granddaughter, Klara had a longstanding affair with Alois before marrying him in 1885 after the death of his second wife. In 1889 she gave birth to Adolf Hitler.