But Father's Day is ONE day, and you know he is a father. Did you really think it was right not to allow him that day with his kids?  Many people plan things last minute, and if you know they do that, the likley perceived your maneuver as attempting to hijack Father's Day.  Next year, go out to dinner with your dad.   YOu say you allow one to one time with them, this would have been a day to do that.  

I am sure you are a perfectly nice person.  Unfortunately, while his kid's treatment of you seems personal to YOU... it really isn't.  It's probably a mixture of a few different things going on.

1.  They have a hard time seeing their father with someone that is not their mother.

2.  You aren't really their stepmother.. because they are adults.  You are their father's wife... there is a little bit more separation there.

3.  There could be things to do with their mother and the split that spill over onto feelings towards you.

4.  They could be self centered kids.. your DH will love them anyway.

I think that perhaps for FD.. you would have been best served by making plans with your own dad.  Your FDH is not your father.. and it's up to his adult kids to make whatever plans... let them fall on their own sword if they fail.  Yeah.. he might get his feelings hurt.. but this wasn't your responsiblity to save him from this hurt... his kids should be stepping up.

What should you expect from his kids?  They should treat you respectfully.  You should be invited as their father's partner to appropriate social events.  It sounds like that is about where you are here.. and that may be all you can expect from them.  It sounds like you have lots of other great people in your life.. save your efforts for them.

Why can't your FH do both?  Since you scheduled something first, that should take priority for FH, and the sskids should work around that, doing something with their dad and then dropping him back off for your celebration AND they are invited (they don't HAVE to participate, but they are always invited).  Why not get them involved with doing something THEY want to do at your house with their father - a special movie, game, music, dessert to make with them.  To break the ice, "2 lies and a truth" where each person says two lies and a truth, and everyone guess which one is true.  Food for thought...

Your definition of family oriented isn't the same as theirs, and that's okay. My DH has VERY different relationships with his parents and brother than I do my parents and siblings. That means we can butt heads around holidays because what I think we should do is not what they want or are accustomed to doing.

Treat his kids like you would any other in-law because, being adults, that's all the more they are to you. Be inclusive with the one who is inclusive. Be distant with the one that is distant. That's fine.

Now, where you have a real problem is with your DH not communicating, and there is likely one of two reasons for that. Either he is bad at communicating plans (my DH struggles with this because he is chronologically challenged while also being a short-term/last-minute planner) or he thinks you'll be hurt when he tells you plans so he just springs it last minute.

If It's the former, then that's your FH and how he operates. There are ways to come up with a compromise, such as you won't plan anything that includes him unless he asks you to include him. Leave Father's Day for his kids to plan. You can do your own thing and keep him informed, and he can figure out how he wants to fit in and who in his family that he wants to involve. If you have specific events/holidays that you want him at, then make that clear upfront what your plan is (building in time for him to spend time with his family). Or, if this is a big sticking point for you, decide if you can live with a FH who doesn't communicate plans how you want him to.

If it's the latter, where you'll be upset, that's on you. You know his family operates differently, and it's not on them to change to accommodate you. It would be nice if they viewed you like a member of the family, but they just may not. It's not fair to your FH to make him feel bad for spending time with his family when they don't seem disrespectful, just different. If they are disrespectful, then that is an entirely different conversation.

After six years, you know what this dynamic is like. Either you and FH are moving toward a middle ground that you both can live with, or you're not and therefore aren't compatible. There may be more that you aren't sharing, but overall it sounds like your issues as a couple stem from having differing views of how to communicate and how to operate as a family. There is a ton of room in that space to compromise so that everyone gets their needs and some of their wants met.

"Dad must of forgotten we made plans", Oh right, his DD had to throw that in. If it were one of their significant others, I bet they'd get invited. I can tell you by personal experience it doesn't always get better, even after you are married

Don't waste your time waiting for it to get better. Sounds like these adult brats are off to a good start in disrespecting and excluding you. So what, Father's Day, Xmas, Easter, weddings, graduations, birthdays, Thanksgiving - I bet they will continue to exclude you no matter what holiday or event they come up with.

This whole business of adult skids not being able to be mature enough and to respect the fact their bio parent has moved on from whatever prior relationship they had. You would think they would be happy for their parent. Oh no, why be happy for your parent when you can act like a spoiled five year old who just wants daddy to yourself.

good luck going forward.

I had hoped for a relationship with my SDs at one time. I too came from a small family and thought that having more people in my family meant more fun. My SDs viewed having me in the family as someone new to scrutinize and make fun of. They are the type that slam other people to make themselves feel better.

It has evolved that I occasionally see one SD, and I have not seen the other in 4 years. I let DH handle everything with his kids. I do not want to spend any time with them, so I don't care if I don't get invited to things. And since they know I don't care, that took the fun out of the game for them. So it has died down into a peaceful situation for everyone.

Before you get married, make sure to define your boundaries of what is important to you. These situations ramp up when you make your relationship legal, because now there's an inheritance for the kids to worry about.

You will never be there friend. Aunt, or whatever.  You have to face that. Fathers Day is a given.  But other holiday your FH has make sure you are included in the holiday. You are invited, you play a role,   This is really a boyfriend problem.  Not a step kid problem.  Your BF isn’t making sure you are respected 

Your planning to have everyone together is what kind people do, being inclusive and trying to facilitate getting the family together, . I get this. The lack of communication from your FDH is something that needs to be addressed. Did he shy away from telling you because he knew you were to be excluded and he knows that is wrong? He knows you would be hurt?

Its utterly ridiculous and exhausting to have to eggshell it around adult steps. When are you getting married? My suggestion if his kids will cause drama, or make you feel less than on your wedding day please ELOPE!!! However prior to your nuptuals please have healthy boundaries in place, and be sure that you and FDH are on the same page. 

Congratulations on your engagement!