If Hitler had any children, and the Soivet got their hand on them, they would have become wards of the USSR, and being well treated while growing up to be the perfect communists. If they ended up in the Westen zone they would likely have been adopted away while their identity was hidden.
I would rather assumed they would land in one of the thousands of foster homes in the Soviet Union (where the children of executed or imprisoned "enemies of the people" were accomodated). They would never been told who their parents were, and would probably end up later in some manual labor job - or simply on the street.