This is a great, reflective post. I'm a firm believer in letting go of any bitterness being held against people or things that have happened in the past. My belief is most times people do the best they can with the tools they have at their disposal. I think forgiveness is a gift you give yourself. But everyone is different. Letting go of that is really difficult for some people. After a while it becomes a part of their self identity.
I often think back to my father, how he was raised in a succession of foster homes (many of which he was abused in) but he never had any blame or bitterness towards his Mom. Although he had his issues he wasn't a mean person either, he was often kind to a fault.
Those sound like some really good and healthy memories! I'm more inclined to focus on the positive things as well. I don't think my family does either. It's just interesting the what and how they remember certain things.