Are most Palestinian families originally from Palestine ?
Yes. We are from Palestine, and I can trace my family to 11 generations who lived in the same exact area we are living in right now.
Update: You will find in one of the answers someone pretending to be a Palestinian living in the Westbank and saying that his family originated from Iraq. That user is not a Palestinian and is using a fake identity to promote multiple outright lies and fabrications about Palestinians on Quora.