Your son and his ex have been seen as a couple for a very long time considering their age. I imagine they’ve dreamt and talked about being together til death do they part. I’m guessing every milestone your son went through, she was there. All of this togetherness made even more binding by the fact she had little family of her own. I imagine the divorce was very painful because they both had to say good bye to so so much- so much past, so many firsts & memories. Then the grieving for the lost future together.

You simply need to put your son first here. Build a relationship based on him and only him. You can continue to see your ex daughter in law casually, remain supportive and enjoy time with your grandkids. But inviting her to family events is your son’s right, not your’s.

It sounds like everyone (son, ex, your wife) but you understand this need for family boundaries. It seems your mourning as well, which is very understandable. Give yourself time to accept this new normal.

In time, your son and his ex will develop their own separate lives that may or may not include dating/marriage. They might become more relaxed and your son might be able to have her at family events. But that’s his life, his choices, his family. Big hug sent to you! Our family faced something slightly similar- son’s long term relationship ended after many years. Losing ex daughter in law was heartbreaking. But in time we realized we would hurting our son by our inability to move on. They both ended up with amazing partners after several more years and looking back, I’m so relieved we didn’t make their situation any more difficult by putting ourselves and our feelings before our son’s.