from wiki
Adolf Hitler was born April 20, 1889 at Braunau am Inn, Austria, a
village in Upper Austria, bordering Germany, the third son and
fourth child of six. His father, Alois Hitler, (born
Schicklgruber), (18371903), was a customs official in
Austria-Hungary on the German border; his mother, Klara Pölzl,
(18601907), Alois' second cousin (presumably), was his father's
third wife. Because of the close kinship of the two, a papal
dispensation had to be obtained for the marriage, both being Roman
Catholic. Of Alois and Klara's six children, only Adolf and his
sister Paula reached adulthood. Hitler's father also had a son,
Alois Jr, and a daughter, Angela, by his second wife. There were no
children by his first wife.
Alois Hitler was born illegitimate. For the first 39 years of his
life he bore his mother's surname, Schicklgruber. In 1876, he began
using the surname of his stepfather, Johann Georg Hiedler, after
visiting a priest who was responsible for birth registries. The
priest declared that Johann Hiedler was Alois' father (Alois gave
the impression that Georg was still alive but he was long dead).
The name was variously spelled Hiedler, Huetler, Huettler and
Hitler and probably changed to "Hitler" by a clerk. The origin of
the name is either from the German word Hittler and similar, "one
who lives in a hut", "shepherd", or from the Slavic word Hidlar and
Hidlarcek.