I think you've tried very hard to be kind to all concerned. If you could go back and do it all over again I would advise you to tell your mom that you are not able to invite her friend to your graduation because that would be unnecessarily hurtful to your father. You had no obligation to let this man come to your graduation.

I understand that you are fine with him coming. And it's fine for you to even be glad that your mother has this relationship. But, for 3 years, your mom didn't even want this guy involved with her sons. Now he's pushing to be at the graduations. Why? That is not what a gentleman does.

If he knows that his presence will be upsetting to your father, then he should be gracious and say he will not intrude on a family event. Your mom has been weirdly sneaky about a lot for a number of years. That should not get rewarded.

Your dad is wrong to blame you for the hurt he feels, but he's your dad, and he's hurting. Has he been a good dad? Does your academic achievement reflect the love and support he has invested in you? If that is even a little bit true, then I would advise you to do the following: tell your mom that her boyfriend is not invited to the graduations. If you are friendly with this man, then apologize and say you are sorry, but you must rescind the invitation. Offer to have a celebratory dinner out with your mother and him on another night. Tell him that you would be grateful for his understanding that you want to ease your father's pain. If he gets mad at you about that, then he's not much of a man, in which case I wouldn't care how he feels.

My boyfriend was previously married. I was invited to his son's high school graduation. If I thought my presence there would have caused any discomfort for the boy's mother, then I wouldn't have dreamed of going. I did not help raise that boy. Celebrating his accomplishment belongs to his mother and father. I would have no right to darken that day for his mother. It so happened that my boyfriend's ex-wife was already in a second relationship. She was perfectly happy to meet me. We all had a great time. The situation in your family is different.

I hope you work this out. You sound sincere in trying to do what is right.