I can totally relate to where you are coming from. I have a very close private family and we never discussed any problems we were having outside of the home. My parents have not passed away, but I always felt tremendously guilty if I shared anything about my family that was at all negative. It's only more recently that I've been more comfortable doing so and I realize it's much healthier to do this. People need to share their feelings and if you did that with friends you trust, there is no need to feel bad. It's part of human nature that we need to share our experiences and emotions and in fact if you didn't do that and only felt you could say the nice things, I think that would be worrisome. You obviously hold your parents in high regard if this is bothering you so much, so I think you should feel secure knowing that you love them deeply and are in fact honoring their memory very well.
Take care.
We all do this. At this point what is done is done and you have to move on. Just don't entertain any questions on the subject with whomever you shared information about your family. Act like it never happened. That's what I would do. No need to beat yourself up constantly about this. Take care.