Adults don't generally hold on to grudges like this 10 years on. I can only assume they've probably seen things from you and your partner that made them decide to keep him out of their lives.

There is no God and even if there was, human beings need to use judgement to make decisions; they shouldn't feel ashamed for it.

If you want to heal your relationship with them you're going to have to talk with them and ask them to accept him as a part of your life. You're not going to get absolution just because it's been a decade, there isn't some kind of statute of limitations on relationships.