Not German? What a strange argument!
Isn't that a bit like saying a Texan is not American?
Hitler was born to a German speaking family in Austria.
He served in the German Army during the First World War, and was awarded for bravery.
Germans of the 1920s & 1930s considered him German enough to elect him to their parliament.
He became Chancellor of Germany and Leader of the Third German Reich.
In 1938 he annexed Austria, making all Austrian Germans citizens of Germany -- wouldn't that include himself?
In 1941, he lead Germany to invade the Soviet Union.
So, in exactly what sense, pray tell, was Hitler NOT German?
Hitler was born in the Austro-Hungarian Empire. Is that so difficult to understand?