In most cases no the grandfather can no longer abuse their grandchild once they are in their mid to late teens because the victim now has a voice to protect themselves. No matter how old the abuser they should be reported to Child Aid if the grandchild is under the age of 18 or, the 18 plus victim of abuse can charge their grandfather with sexual abuse to the police.
No one does know for SURE who his grandfather is. Adolf's grandmother was pregnant and not married at the time when she concieved Alois Hitler (Hitler's father). There are no documentations about who he is. There are about three theories. One is that the man WAS in fact Jewish. How ironic. I do not remember the rest. Sorry :(
There is no historical evidence to suggest that Hitler was Jewish. Recent scholarship suggests that the rumors about Hitler's ancestry were circulated by political opponents as a way of discrediting the leader of an antisemitic party. These rumors persist primarily because the identity of Hitler's paternal grandfather is unknown; rumors that this grandfather was Jewish have never been proven.