A dominant thought is one that you focus on all the time, so in the case of your parents, maybe not so dominant - as they rose and fell.
It is wonderful for you to acknowledge your love and appreciation for you parents, and the love that is shared between you, that is really something worth focusing on as a dominant thought.
Whatever emotions you're feeling, just acknowledge them, accpet yourself "I am where I am and that's OK" and just find a better feeling thought. You're looking for relief.
It's not possible to jump from guilt to joy in a single step. You can move yourself up just by finding a slightly better feeling thought .. even if it's moving from guilt to anger to blame .. then move up to optimism etc.
You know you find a better feeling thought (better vibes) when you feel some emotional relief.