Hi there,
This question comes up a lot, and ultimately the premise upon which it is based - that the Holocaust or Hitler's hatred of Jews stemmed from some personal event or experience - is not supported by evidence. Anti-semitism in German and Austrian culture during Hitler's life was was pervasive and helped shape the man and his narrative of racial prejudice.
The following answers go into detail in addressing your question and its premise, and will hopefully be of interest to you: