"it is 100% disproven BS."
Not sure where I heard it first, but it seems like it was from a few different sources. Do you have any links that clear it up?
Well, his nephew's name also was Hitler, that pretty much clears up the name issue.
I will refrain from casting abuse on those sources but I would bet they share a certain commonality.
The wonder of the Internet is that you could have found the answer yourself from legitimate sourced references by simply searching the statement: "Hitler was not Jewish"
One example:
http://www.holocaust-history.org/questions/hitler-jewish.shtml