AIBU to not invite my 20 year old son on a trip with his siblings?

No the daughter will have made her decision in the context of her parents behaviour just like your children did.

And the answer to that is, that's not your business and I can't make any promises it won't happen, but I hope you'll feel differently in future. Not to ignore his attempts to communicate and exclude him from family events.

If the post represents a real situation, I suspect that a moratorium on discussing the breakup, the responses, the allegiances during some planned family time would be a healthy thing.

So basically you got angry at him for picking sides, so you're now picking sides.

Yabvu. Your poor son, yes husband dad was shitty to you but ignoring him because he chose to live with his Dad is horrible, as is not including him in family things. Kids shouldn't have you pick sides like this.

Barely. And OP is also his parent.

This is on OP. But tbh if she can’t see this without posting on here, doubt she will. She’s been asking them to choose from day one, and she’s even hot the siblings to follow suit. OP should look for support from her family and friends, not her children.

Deplorable.

His sisters graduation will have been her choice.

when my kids graduated (and we were in a difficult divorce situation) my DS decided not to graduate in person because he just didn’t want to deal with all the family shit and the inevitable rows.

my dd graduated in person but gave both me and her dad specific instructions as to which bits we’d be allowed to. Her dad negotiated a dinner the previous day with his new family (which she bitched about but went to).

divorce can really fuck sibling relationships as well and if there is a lot of drama going on there then op wasn’t necessarily wrong to not take the son on holiday.

i do think you need to reach out to him separately though op and rebuild a relationship,

What an awful situation for everyone - but mostly for your son.

I can imagine how very hurt he must have felt when everyone (even the cheating father) went to the graduation except him. Same with the holiday.

Poor kid. Do everything you can to put this right now before you end up estranged.

He tried to reach out but 'yiu went quiet in him' He was what? 19 at the break up, went with his dad, tried later to reach out but you rejected him ...secure in have all 3 other siblings on your side. It was lovely that they supported you after your husband cheated after a long marriage ...they are LL angry with their dad ...naturally ...but your daughter chose to invite her dad, the cause of the marriage break up rather than her brother? I can't get my head around that choice ...punishing your son again for his choice of staying with dad ...yet inviting dad and not him. What a hurtful snub for your son. Daughter saying ok dad ...you cheated, broke us all up, but I'm prepared to reconcile, forgive enough to invite you to my important occasion, but not the son whose crime was to stay with you. Then he isn't invited to the family holiday. He seems to being made the scapegoat for your husband's crimes. He made a poor choice, but why is he excluded when your cheating husband was included.

"He's told me he doesn't think he'll ever be okay if I date or remarry one day."

But it's okay for his dad to do it?! No. He's being manipulative and immature. You need to let him know his attitude and comments are not okay and do not reflect reality, but he might not be able to accept it, sounds like he is firmly in the victim mindset here even though you're the victim.

So he’s tried reaching out a few times and you’ve ignored him. You didn’t want them taking sides but ghosted him because he chose the ‘wrong’ side. I understand you’re hurt, but the person you should be angry with is not your son. His siblings are simply following your example. He’s behaved like a petulant teenager - at just 20 with his entire world collapsing he’s allowed to feel and behave like that. But you have been appalling to him, utterly awful.

He was young and shouldn't have taken sides tried to reach out to you and you ignored him. No wonder he is upset. I bet he feels like the black sheep of the family. Nasty dynamic. It seems you only want family who take sides for you.

You are expecting your son not to love his father unconditionally

You are suggesting with your actions that you don't love your son (or his siblings) unconditionally

Maybe you don't, but it is a dreadful thing to try to turn someone against a family member for offences against you.

Her son is an adult too.

Where did I say its all his fault? He does need to accept that his words were inappropriate and unacceptable and that his father broke his family up not hos mother.
He's 20 not some child and should know that his demands are quite frankly outrageous

A very young adult experiencing stress and possibly trauma he’s never dealt with before.

And whatever decision he makes doesn’t have to be permanent. Doesn’t deserve alienation from his mum and siblings.

'He's an adult who chose to stay with the person who broke up his family'

This really stood out for me.

Oh my this is a very sad read , that poor boy ☹️Step up and do something @vhydr , you are the adult in this mess .

This

YABU For ignoring your son when he attempted to reach out several times.

It isn’t your fault the family fell apart. But it isn’t his fault either.

My parents divorced when I was 18, and they made us feel guilty if we expressed any kind of loyalty or love to the other side. It was horrible. We had nothing to do with the divorce but they took it out on us, which is what you’re doing with your own kids right now.

I understand you’re feeling a bit raw but your son didn’t cause this mess, so it’s extremely unfair for you to take it out on him. Yes, 20 year olds can have a bit of a black and white vision, but you won’t get him to see your point of view by pushing him away. Stop punishing him and start being the adult here.

He’s an adult and he’s experiencing the natural consequences of his choices.

It sounds to me that the things he has been saying are him parroting what he’s heard from your ex. The ex will probably have spun him some stories to paint himself in a better light, and now DS has been caught in a proxy battle that isn’t his to fight.
This age is often the hardest for kids of a separation- people expect them to be ok because they are supposedly grown up but it is incredibly destabilising for young adults who are about to spread their wings to not have a nest to return to.
You have had some harsh responses here OP but I hope you can take on board that you could have done things differently and to repair things with DS there are some apologies to be made. Be open and curious with him, ask him why he thinks these things. Explain your side of the situation with DH, not in an accusatory way, factual and honest about your feelings. He is a hurt confused little boy and you are his mum - I hope you can all find a was to repair and reconnect after Ex blew up the family.
Another thought on the psychological aspect of why he chose to stay with dad initially. My first thought was that dad manipulated him and played the poor me victim card. But also it could have been that he was less secure in the relationship with dad so felt the need to hold on to and strengthen that one thinking that bond with mum was safe/secure; but then devastated and angry when that turned out not to be the case. Your therapist should be able to help you work this stuff out… I am guessing because I don’t know the e people involved but saying this because these are common patterns.

No.
"My eldest tried reaching out a few times and I'll admit I went quiet on him for a bit."

The estrangement is absolutely not all the son's fault. The OP needs to accept some responsibility as well.

I mean he vs might be an an absolute arse - I can’t see things improving if you (both) carry on the way you are. If you want to not have a relationship in the future then you should carry on. He’s 20, and has 3 siblings.

You can explain the breakup without dumping all your emotional reactions on your child like that. All that stuff about your hopes for the rest of your life is for friends, siblings, therapists - not for your child who is having to readjust his own expectations of his life.

Relationships end. The marriage is over. The question is whether that has changed your relationship with your child. For most people, it doesn't. In this case, the OP seems to have recruited her team, reacted frostily to the child who didn't sign up, neglected her relationship with him, and undermined the relationship with his siblings.

Plenty of people go through marriage break-ups. Enlisting your children to listen to your regrets and traumas is not the right way to handle it.