To have nothing further to do with them?

@Pouticel does your husband have the only car in the whole extended family?

Wishing you well @Pouticel . That sounds like deliberately hurtful behaviour from your DH's family.

And I think you are being fair when you say NT people actively exclude ND people.

Time to move into acceptance that what you wanted for your child isn't going to happen.

Put your effort into your happiness and growth, and that of your child.

They stopped coming for Christmas Day with us and PIL a few years ago anyway. Don’t know why. DH takes DC and PIL to their house on Boxing Day but I can’t fit in the car so I don’t go.

I don't think it's that unusual to want to be just with your young child at home.

Do you have a very small car?

Do you have a really tiny car! Two adults in front, two in back with dc!
Unless it’s a six hour drive surely it’s doable.

Why don’t your DH and his sister do year about?

I think it is hurtful as there is only one cousin, but I also think that you are extra upset with high expectations for these children being a support for each other.
Are you worried about your DC being alone as an adult.

To be fair I was very close with all my cousins as a kid. But soon as we got to late teens we had nothing to do with each other . And 20 plus years later thats stayed the same.
We are all very different people on different paths . I dont think all cousins are close at all.
Most just see each other at maybe grandparents life events and thats it.
I would just accept and move on . Your dc will make friends in school . They are the ones they will be close too.

Also bugger being left alone every Boxing Day while your family go off on their jollies without you. I'd be nipping that right in the bud.

You're being too generous about letting them force you to stay at home. How far is the drive?

thats my opinion. You don’t have to agree.
but if you’ve agreed and the orphan shows up at your door, to say no cos your kid wasn’t invited to a birthday party… seems out of order to me

What a vile response when the OP has said exactly why she feels this way. Talk about kicking someone when they’re down, I hope someone does this to you, you must be unhappy?

OP I can understand why this is upsetting. I guess it’s worse because it affects your child and you have tried and you actually don’t know what the issue is…
What I would say if I think you should pull back, completely, and see if they contact you. If they do, you should say oh sorry I’ve not been in contact but I just thought you weren’t interested, then they might elaborate on why; if they don’t contact you, then at least you made the right move not to bother with them and you can go away knowing you made the right decision.

The only thing I will say is there’s usually a reason for the lack of contact. We have actually cut off my SIL and BIL (DH’s sister). And we have kids of a similar age. We can’t deal with BIL, he’s just a total dick head, competitive, not a nice person and bad company and we don’t want our kids around him. Could it be that they don’t like your DH?

I don't think OP is being overbearing. She is merely facilitating a family relationship.
I can really understand how you feel OP

You COULD go with them, someone does not want you to.
Maybe its them or maybe its your DH

Everyone else has mum friends and their kids play together. I can accept myself and DC being excluded by others, but it’s hurtful when family does it as well.

I think that you are placing too much importance on family tbh.

That they have to get along & have to spend time together.

If (for example) you were difficult to get along with or always causing upset why should family have to put up with that any more than anyone else?

I have one sibling who I get on well enough with.

I wouldn't say were are close.

I have friends whose company I much prefer.

That’s bizarre. What conversation did you and your husband have about this? Is your marriage happy?

Am I allowed to ask why the OP didn’t just say something when the little boy mentioned his first party. To me her response when she found out about it is well over the top, unless of course there is a huge back story that we haven’t been told about.
I can understand why most of the posts on here have attributed the increasing distance between the cousins down to the OP being hard work, and I also agree that there’s no written rule that cousins have to socialise or be invited to each other parties, but I can’t get my head round the fact that his parents thought it was OK to keep the whole thing a secret (and to tell their son not to mention it, if what the OP has said is true), especially bearing in mind the boys are the same age and have socialised previously. To me that’s just rude and pretty poor parenting. I suppose it could be argued that they didn’t want to cause upset, but if that was the case it’s completely backfired.

Kindly OP, I think you are suffering with RSD as a result of being ND (I say this as someone ADHD who suffers herself!) and this has caused you to react very strongly.

I am sorry you had a lonely experience as an only child, but that is not a given for all only children. What about an individual's personal relationships, both romantic and platonic? The only company doesn't have to be from family. There are plenty of people with lots of siblings and family who don't have close relationships with them, they're not necessarily lonely either.

The fact is- you want your DCs to have a relationship. For whatever reason, they don't feel as strongly about that as you do. I have a few cousins who I spent a lot of Christmases etc with growing up who I barely ever see now, we are certainly not friends as adults just because we're cousins- I suspect there are lots of families who are the same.

At 7 your child has so many opportunities to make friends and form relationships on the horizon. Stop trying to force this one, but don't cut them off either- if your DC does decide they want a relationship with their cousin, they won't thank you.

I’m torn here. On the one hand, we’ve always hosted separate friend parties and family parties so I wouldn’t be upset about that. On the other hand, it is horrible that you’re left alone on Boxing Day, assuming you’d actually like to be included.

An all school party where the other kids know each other + one cousin who you haven't seen for 6 months would be awkward, mainly for the invited cousin. OK, they shouldn't have turned it into a big secret (pretty hopeless with a 7 year old who will tell and did tell) but you could talk to them about it without WW3 breaking out from your side. It won't help.

As far as saying you wouldn't take their children if the parents both died, it doesn't speak well of your true sense of family. It it's just because you're angry at the moment, for God's sake don't share it with them. It won't be forgiven.

Does the cousin have other cousins on their dad’s side and therefore the parents don’t worry so much about who the child will have as family when they grow up? Could they be closer to the other cousins rather than your child?

I can see why you feel hurt OP, but wouldn't that be punishing both children for something that isn't their fault?

‘I’ve always encouraged friendship on the basis that eventually they’ll be each other’s only family’

I’m sorry, but is it only me finding the wording of this weird? They’re 7 year old children, you can’t force them to have a relationship on this basis. No doubt they will both eventually make families of their own, not everyone has a close relationship with cousins as they reach adulthood.

What?! You are left alone at home on Boxing Day? That's awful. No wonder you are so triggered about being left out as an only child! Why can't PIL make their own way there, or BIL/SIL pick them up so you can go in your own car? Why can't the car take five of you - even with a car seat you should still be able to squeeze in two adults unless size is an issue for one of you?

I'm starting to suspect you have a DH problem. Does he see BIL/SIL independently of you at other times? What's your marriage like generally?

You need to grow up and get some therapy frankly before you pass your insecurities onto your child. Their child doesn’t have to be friends with your child. And I’m not surprised they back away with some of your replies. Please go and seek therapy. Your child will make other friends. There’s nothing wrong with being an only child but you can’t keep pushing them onto family who clearly don’t see it as anything other then pushy and uncomfortable.