Yup it's totally fair. Being a shoulder to cry on is different than what the OP sounds like she's doing. And add to that being a people pleaser. Enough people have said to stay out of it, let it be, let it go. Seems fairly clear that the OP is overly involved in the intricacies in the adult children's lives.
She clearly says that she told her oldest son to leave her out of it. She never says in the OP (has she even posted again?) that she DID anything or even gave an opinion to her kids. Two talked to her about being upset. One talked to her about being upset that they were upset. She said "work it out, leave me out of it". Where does that say over involvement to you?
Yes, everyone here just about has said "stay out of it". Where has she indicated that she had done or plans to do other wise?.
1) No they've been divorced forever and both remarried. My husband calls his stepfather dad as well. He also has a half-sister from his mom's marriage to his stepfather
2) Yup
3) Nope it doesn't make a huge difference in this context. You're really missing the point in my comments. In the OP the OP makes it a point to drive home the point that some of the kids weren't invited. She then goes onto to discuss a bit of the relationship with the children. Not every relationship, especially as you grow into an adult and into your adult life, is the same between siblings and their parents. Not inviting all 4 adult children doesn't equal a travesty maybe even moreso given that the father didn't see the children much until they were adults and from the comment "He says if they want to see him, they know where he lives." sounds like it's a two-way street at least nowadays.
If a parent chooses not to have a relationship with his kids for 20 years, to have one now is on him. And yes, it is VERY different from your husband's situation. Unless you have seen it first hand or been in the situation, you may not understand it but it is very different. Its a far cry from a healthy parent/adult child relationship.
In the real world not every parent shares the exact same interests and bond and relationship with each of their children and in the real world not every child shares the exact same interests and bond and relationship with each of their parent. And in the real world not every sibling shares the same interests. Parents try to be as equal as possible generally speaking but it doesn't mean everyone is going to have the exact same relationship. Sometimes you just aren't going to be invited and sometimes you'll be the one invited when someone else isn't.
No, of course every child and every parent doesn't have the same interests. But as a parent you don't decide to pick and choose which child to "bond with". That is selfish and hurtful to your children. "Parents try to be as equal as possible" but Dad isn't doing that nor has he ever apparently. Besides, Thanksgiving dinner doesn't really have a whole lot to do with shared interests. Its supposed to be about family. I have three kids all with different likes, dislikes, beliefs, interests, etc. And yet, I find a way to interact with all three. Its not hard, you love them, they are your children; you just do it. Heck, even the father of my sons can find a way to do that and he isn't around more often than he is!
Sounds like the bond forged by the eldest son and the father is strongest at least right now. Don't get me wrong I've got empathy for the whole bit but if I were hearing from one of the adult kids it would be more helpful.
Again you're really missing the point. I did say "I don't say biased in necessarily a bad way". If one of the adult children were writing the OP it would be a lot different. Here the very situation being described is inheritantly biased and more so than normal based on the OP's history with the father and various facts. The OP also appears to hold on quite strong to these past issues/incidents/variables; makes it quite hard to get a less colored viewpoint.