How do I stop feeling guilty for my parents actions?

Wow, I was found on face book by at stepsister from 25 years ago. My parents were really messed up, both going through several marriages each. Lot's of partying, neglectful of the children involved. Us kids got scattered in the 70's. Me ending up going through the foster system, because neither parent was fit. I have married, raised a family, and been blessed with the ability for building my own life.
I put myself through school, did it all on my own, until I met and married into an awesome family.
Yet I still feel extremely bad when I meet up with people from the past. My parents past. Because they were so thoughtless of others. I have encouraged my children to be independent, accountable, not victims, and always count our blessing. Life's had it's up's and downs, but it had made me a woman happy with who I am. Until the ghosts in the closet come a knocking.
Mom and Dad's ghost Haunting me. It sucks really. I guess I'm just venting. History just can't be undone. Still haunted.