Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
I am very sorry to know about this painful situation.
This is very sad and frustrating, since it shows how your loved ones cannot share all together with you as a real and healthy family, because of past mistakes and your husband's rigidity and unwillingness to forgive, understand and move on, focusing on what matters the most.
I can imagine your frustration and sadness because of it, but only you know how painful it feels to be in your shoes, and without doubt, your feeling are valid, real and justified. He is an adult, continue to be their father but chooses not to forgive and give them a new chance. They have already changed her ways and taken initiatives to reconnect but he refuses to let it happen, dismissing the need them, you and the children have to enjoy their family together. You feel hurt, and I'd say betrayed by his decision not to be part of her lives any more, that's overwhelmingly painful for most people in your shoes, and I believe the resentment from it is totally valid, since there is nothing in the present that could justify him perpetuating his attitude. He needs to come to terms with the fact that their are both individuals and have the right and freedom to choose their own spouses, and that now they, their children, you and the whole families need this unity and harmony he's been denying for this long.
Your expectations are not selfish nor unrealistic at all but normal and fair.You feel hurt because your husband chooses to perpetuate this sad situation without a valid reason, because of his own rigidity and limitations to assess reality, to forgive, to value the importance of what you all are missing here, and this can never be easy to face. You are literally grieving and feel hopeless since you know it totally depends on him, and he is choosing not to allow your family to experience and enjoy your lives together, that's very immature, selfish and shows his personal issues an immaturity getting int he way, affecting all of you.
This situation is specially painful for you since it triggers feelings from your own experience with your father, you know how unhealthy and destructive it could get and you do not want that for your family. Unhappily, I believe he's acting out his personal issues, the ones he has from his own personal experience with his own parents and family, and since he has unresolved feeling from those situations, he self-sabotages ans sabotages your family with it.
I see you have been doing the best anybody in your shoes could do about it, but he is the only one with the power, and the responsibility to make changes happen, to change his mind, heal his heart and work on the relationship with them. I think individual counseling would be necessary for him to work on his personal issues leading to this serious family problem, but if he continues to be unwilling to acknowledge how dysfunctional his approach has been, and how his choices and actions negatively impact everybody here, there would be no hope for any significant improvement. I hope time and life experiences could promote his insight and soften his heart for him to allow himself and your family to share all together as it should be, as you all need and deserve.