Adolf Hitler was the third son and the fourth of six children of Alois Hitler (born Schicklgruber) (1837–1903), a minor customs official, and Klara Pölzl (1860-1907), his second cousin, and third wife. Alois was born illegitimate and for the first thirty-nine years of his life bore his mother's name, Schicklgruber. The name Hitler appears in the maternal and paternal line. Both Hitler's grandmother on his mother's side and his grandfather on his father's side were named Hitler, or rather variants of it, for the family name was variously written as Hiedler, Huetler, Huettler and Hitler. Because Adolf's mother was his father's second cousin, an episcopal dispensation had to be obtained for the marriage.
William L. Shirer