Austrians are Germans.
When the Habsburg Empire broke up, they originally considered calling the rump part of Austria "German Austria", but then that got confusing, and they just called it "Austria".
The only reason Austria isn't part of Germany is that, before WWI, it had its own little Polyglot Empire with the Hungarians, Slovaks, Poles, Czechs, etc. After WWII, they weren't allowed to join with a divided Germany again, and Austria got away with claiming they were Hitler's first victim and not open collaborators.