Actually a diagnosis is very necessary. You don't get to take an online quiz or fill out a checklist and armchair diagnose anyone. It's not ethical and it's usually wrong.

That said, I'm sorry your mother and father were abusive and unloving. Do your siblings claim that your parents never abused you? My step sisters say that about my relationship with my parents and it sucks. It's why I don't talk to ANY of them anymore.