In Austria there actually exists an Adolf Hittler (with double-t). Though, I’m not sure if he is still alive, he was quite old when TV made a small interview with the guy some years ago. He is (or was) not a Nazi but just didn’t want to change his name.
Naming of children in Germany isn’t really that easy sometimes (if you want the child to have a unusual name). The authoroties have lists with “legal” names. So offensive names are illegal and also names that will affect the childs well-being negatively. So it was ruled that it is illegal to name a child “Winnetou” (the american Indian from the Karl May stories - maybe unknown outside Germany?) or “Windsbraut” (bride of the wind). So also names like “Harmony” or “Charisma” might be illegal here. But I’m not sure about this last point.
Concernig the name “Hitler”. Searching the German phonebook www.telefonbuch.de gives no entries for “Hitler” but some 34 entries of “Hittler”. I don’t think it is illegal to be called “Hitler” for one’s last name but probably all Hitlers left changed their names (or at least have secret phonenumbers now).