"Me and [DIL] are never going to let our children go through the same that we went through as kids, unlike you we are good parents."
It must be very painful for you to read that Jane. But I am guessing that you do know what he is talking about - for him to feel so very strongly about this implies that either he is totally insane and irrational or something pretty serious has happened, whether as one incident or an ongoing problem.
Has he never talked to you about what this is all about? Were things OK t some point? Can you discern when the change happened and what might have precipitated it?
I do think that you might find counseling a help for lots of reasons. You may have no choice but to come to terms with the situation and move on, in which case a counselor might be able to help. Or you may deep down know what this is all about and be helped by getting it off your chest.
His unhappiness seems to be directed at not just you, but your OH and your DD - so there must be some common factor here, and only you can know what it is.
Your son must be suffering too in his own way to have such strength of feeling after so long; and as for your DIL, this must be a very difficult situation for her.
I really do think that you need an outside objective ear on this - someone to whom you can be absolutely transparent and honest, who can help you to get on with life and leave this painful business behind you.
I know that I felt unhappy about my children having too much contact with my parents, neither of whom were bad people, but they were in a bad marriage (at least from the point of view of being a child of the family) - their mind games were quite destructive as a child. However, my children did have contact with them and they proved to be better grandparents in the main than they were able to be parents, and I am glad that they had that opportunity.
But what I do remember very vividly is my strength of feeling about not wanting my own children to feel the same discomforts as I had growing up; so I feel something of your son's dilemma. It is not impossible, if I had let myself go, that I could have written something similar.
Rather than try and talk about things, it probably feels easier for him to just push you away and close the door on it all and get on with making his own way. I know that as an adult I never really confronted my parents with the problems of being brought up by them. On one occasion only when I had not contacted them for a while, they realised something was amiss, and I talked about the incident that had occurred in front of my children that had made me draw back. They were I think quite shocked and took pains not to let it happen again. I do not know whether they made the connection as to how I might have felt as a child on the many similar occasions. We certainly did not talk about it. They were both in their own ways decent human beings and I was given every material and educational opportunity - they were just a very bad mix - although they were very interdependent.
I think what I am trying to say is that this dreadful scenario does not necessarily mean that you are a bad person. There has been something about your son's relationship with you that has gone wrong, but you need to come away intact. This is why you need to have some outside help to get through this sad situation. I hope that you can move on and find some peace. There are times when we have to accept that things will never be as we might wish, but we find ways of moving on and getting on with our lives.
I send you every good wish.