Thanks for coming back in and talking to us some more, Jean. FWIW, I don't believe any therapist ever says anything like, "Yes, you have terrible parents." They might have agreed or sympathized w/ some of your son's complaints (and remember the therapist only knows what he has told them). But I doubt they would write you off as "terrible" w/o even meeting you. That's your son's interpretation.
I'm not sure why DH's retiring would have such a major effect. Is it b/c you could no longer help out financially? Or your son just doesn't like change? Or??
Regardless, I'm sorry to say it but I would back off from ES (estranged son) as much as possible for now and give him space to deal w/ his demons, whatever they are. Hopefully, in time he'll reach out to you... Patience... Hugs!
Ann, I feel for you, as well. I can't imagine why ED (estranged daughter) would turn against you this way after you had such a good relationship w/ her, her ILs, etc. Perhaps she didn't find it as "happy" as you did? Or maybe there's a problem in her marriage she's not comfortable sharing w/ you?
But you said you don't want to consider explanations, etc. Just want to be able to maintain a relationship w/ your GSs. I don't blame you, but IMO, that may be hard to do. How would you and ED make arrangements for you to see the boys if she doesn't even respond to you?
But like others, I suppose you are talking about going to court. Unfortunately, to my knowledge, those cases are hard for GPs to win. And even if you did, the situation would very likely be awkward and strained since there would still be tension between you and ED. And while others are talking about the money your ED and ESIL would have to spend, please don't forget it might be very expensive for you, as well. Sorry to sound so discouraging, just trying to give you a realistic picture. Only you can decide if you want to go down this route or not.
Regardless. I take it your depression was a response to this situation. I am so very sorry. I hope you have been receiving treatment for it, and that you spend time focusing on your own wellbeing. Hugs!