I'm sure I'm only saying what others will: disengage.  The good news is that these "kids" are adults and you don''t have to endure visitation. You, like most people here, had fantasies of being a warm family member.  They have their COD (children of divorce) mindsets and arent going to change.  It's not personal, you could be Mother Teresa and it would be the same.

It sounds like your BF is a sensible, good dad.  He can keep trying to have his relationships with them, whatever.  You have zero responsibility here.  If you are in their presence, be polite and civil.  That's it, you're done.

It's sad for all of us when we realize our good intentions aren't wanted.  That's tough but steplife isnt easy.  Good luck.

There's one question that I have to ask because it would explain a lot - were you the cause of their divorce? If you were, I can understand why his ex is refusing to acknowledge you and poisoning her kids towards you (people can and will hold grudges for decades). If you weren't ... well there's something wrong with the lot of them and you deserve so much better.

"Hiding in plain sight" is a very good expression for what you did at the funeral and it must have made you feel dreadful - an outsider, a pariah. If there is ever a next time when you have to be in the vicinity of these people, do not make any effort to comply with their unreasonable expectations, just be your usual pleasant, friendly self to all around and do not move away to avoid them. Let the buggers deal with it. You are not the problem, they are.

I'm afraid II'm not known for my subtleness nor tact and have to admit that I would have been very tempted to gush at the SD "oh my dear! I was SO sorry to hear that your fiancé broke off your engagement! You must be devastated!" and would have made sure to do it in front of her kids. What a load of crappy lies, whispers and untold truths they all hold between them. Sickening. I hate the mindset that if you don't talk about something it doesn't exist.

What would your husband do if the next time you have to be with them is for a wedding and his son/daughter refuses to invite you? Would he go without you or would he put his foot down? 

unfortunately, OP is being punished for the sins of their own father... he abandoned their mother.. and so him moving on and anyone attached to him becomes poison and to be nice or welcoming to his new wife is a sign of disloyalty to their mother.

The one and only person these kids should be angry with.. and if they feel so strongly.. estrange themselves from is their FATHER.  

I know your DH is a conflict avoider.. but I would so like to have him tell his kids.

Look.. I was the one that left your mother.. I did it because I was unhappy in the relationship.  Now that you are adults, you should understand that sometimes relationships become so broken they are not worth saving.  I know it hurt you.. and your mother and for that I am sorry.  BUT.. my wife had zero part in my decision to leave your mother.  I did not even meet her until many years AFTER I had left.  If you want to be mad and angry at ME.. fine.. but you will NOT continue to have a relationship with me and treat my wife as a Pariah.  She is a lovely person and has no fault in this.  If you cannot fully accept her into my life.. accept that I have chosen to have her be part of my family.. and by extension YOUR family.. then I regret that we won't be able to be in contact any further.  To be clear.. I love you very much.. but I will not tolerate continued poor treatment of someone I love because your mother is still upset about my leaving years ago.  If you want to punish and blame?  that can go on me.. and honestly.. your mother as there certainly were things from HER end that contributed to our relationship's demise.  but you will not punish and give my wife the cold shoulder.. you will not force her to lie about our relationship.  I am done playing your games.. grow up or get lost.

Your DH has to handle his kids. He not doing that. He playing there games. Not introduced you. Making you an outsider, 

You are right I would not attend anything the kids are at. I would go and arrange for a spa day for myself. As DH attends funeral. Or go to a fancy hotel and used some of there fancy services as he attends. 

Before I comment on your situation I just have to rant. I literally can't stand people not being the bigger person and just refuse to get on with it. I hate toxic BM but I'm not teaching my DD to be rude by shying her away from BM if she is there at a family function. Unfortunately she is the mother to DD2 siblings, and it is what it is. If there was a family event I would explain to DD who BM was, and if we have to be civil for the sake of everyone, teach her to say hello and leave it at that. Massive IF that day ever happens. Probably won't be until the skids 21st birthdays or weddings. 

It's so immature of these adult children to hide their children away from you because they don't want them to meet you. You are their dads wife, partner, whatever and they need to respect that. What is that teaching your BF grandkids? That it's ok to be a rude POS. Ugh these people annoy me so much. I'm sorry BM is a train wreck and has serious mental issues. Sounds like she's done a fantastic job of enmeshment. Your best option is to definitely disengage, and it's about time your BF calls them out on their disgusting behaviour every time and not let them get away with it. I guess damage is done it's just disappointing. 

You have been with your BF for 11 years.  If this were me, I would remain boyfriend and girlfriend until he can prove to you that he loves you enough to have your back, will not allow disrespectful behavior toward you, and demonstrate to his kids that you are his top priority.  Period.

They are acting like this as adults, whose parents got divorced when they were adults. All this is to say that they are mentally children. If they can't see that relationships end and their mother is being unreasonable in not accepting the end of her relationship, then they will always behave in such a childish way toward you and your BF. 

I suspect their childhoods were a bit chaotic with a histrionic mother and passive father and they likely didn't develop good emotional regulation and coping mechanisms. They seem to be taking their frustrations out on their father...perhaps because their mother is so emotionally needy and volatile? 

Are you close with your BF's family? What do they think of the whole thing. My advice would be to find some allies in his family, not to conspire against his children or even commiserate with over their behavior (in fact, I would recommend not talking about their behavior with his relatives), but rather to serve as people you could socialize with at these family functions to avoid the drama. Let his kids spiral on their own without being part of the drama. They will never come around to you, no matter what you do, because they feel the need to "punish" their father, which is really only hurting themselves. 

You know what FlowerMom18 - I actually think they are doing you a good service. You are in a situation where they have clearly rejected youand there is nothing you can do about it. Everyone sees it and thinks its horrible. This is excellent. What's much worse is when the situation is "gray" the SKIDs are expectant and extremely nasty towards a SP- everyone doesn't see what the SP is experiencing and the SP gets depressed about having to tote the line and be a personal slave. Here, you've been given a blessing - you literally don't need to get invovled in that mess, they've created boundaries that you are respecting and you can simply not care about them whatsoever. This seems like a really great situation - from my perspective. Hope your mom heals quickly and focus on those who you love and love you. I'd say you won the stepparent lottery when it comes to SKIDs bad decisions ! Go enjoy your wonderful life - eat well, laugh out loud and dance your a** off at the next family engagemetn with all those that like you. :D 

you and your family on your loss.