To not want to invite In-laws other half to birthday party?

Doesn't sound like fun for any of your nephews.

First they discover their dad has another family they didn't know about, & then their mum starts a punch up/gets lamped by a drunk, depending on which mother they have.

You can't have the 8yo AND the twins at the same event if they've never previously met, regardless of whether their mothers are there.

I'd cancel the whole thing & go for tea & cake with the gps on your side, tbh.

This

You want to avoid a Jeremy Kyle / Eastenders drama

I'd cancel the party altogether

But, if you do go ahead with this shitshow, please update on here and I'll be waiting with my popcorn 🍿

We also don't want to be put in an uncomfortable position where she starts asking questions about the twins mother etc, we only found out when she did as it was kept very hush hush and only in-laws knew about it.

First off I would cancel the party and celebrate DC first birthday with a day out at the zoo with my own parents.

Secondly I would be taking a good long look at my in-laws and start wondering if they were keeping secrets from me about my marriage. You have seen how they treat the married-in's, I would be paying attention to that.

Why would anyone think a large family gathering is the best place for secret siblings who have never met before to meet for the first time. Have the party and make clear neither woman is invited. Children can come but they must have met each other first or none can attend as it would not be fair for them to be put in that position.

So hang on. There's an 8yo with one woman and twins with another. These kids don't know the others exist. And now each woman expects that she and her kid(s) will be invited to your baby's birthday?

So are we expecting a big showdown where some of the kids realise they have half-siblings for the first time at the party?

Plus the two mothers shooting daggers at each other or worse?

This is mad. How do you normally facilitate relationships with these different sets of your BIL's kids? Have they met your baby before? How well do you know either of the women?

I mean, fuck this. This is literally your BIL's problem for not keeping it in his pants. His drama doesn't need to be your drama.

I'd just be going away for the weekend. A one year old won't remember the party. But you and everyone else there - including other children - will remember if the shit does hot the fan.

Cancel the party and deal with your completely ineffectual husband. He is your problem. A massive one, I might add.

Just read your update. In that case don't invite their children, then there's no need for any of them to come. You could lie, and say it's just cake with the grandparents only. But remember not to post it on social media afterwards. Or you could simply go away as a family!

None of this is your problem, OP.

If your BIL is getting it in the neck from the mother of his 8 year old, he needs to grow a backbone and tell her to wind her neck in. He needs to tell her that she is not invited to the party because she is a lairy gobshite who threatens to stab people and you don't want that kind of behaviour at your baby's birthday party.

If he's getting in the neck from the mother of his three year old twins then he probably should have thought twice about having unprotected sex with a random woman who might turn out to be as batshit as the mother of his older child.

He has made his bed, he will have to lie in it.

This is very much not your circus, and his monkeys are not fucking invited.

Have the party if you want to. Don't feel you can't celebrate your child's birthday in the way you want because of these nut jobs. But don't tell them when or where it is.

Yeah this, if it's a kid's party, people shouldn't be getting pissed anyway.

We had a glass of champagne to celebrate keeping a small human alive for a whole year. I agree it shouldn't be a knees up though.

Both me and my husband feel that we don't really want to invite her as she has a really bad problem with alcohol and is known to get very rowdy when she has had a drink and can get quite aggressive.
She has glassed people in the past and has been on tag.

I feel you should definitely invite her and then report back how it all went.

Why would you have alcohol at a party for a 1 year old?

The whole thing sounds like a car crash of epic proportions waiting to happen. Don't give them a forum to have it out on your dime and your baby's first birthday. Cancel the whole thing. Reconsider in a few years when your baby is old enough to understand what a birthday is.

Book a nice restaurant with high chairs for you, baby and your other half.

OP what happens when it's one of your BILs children's birthdays?
Does the OW and her children attend? I doubt it.
So why is it expected that she attends your child's party, with who there is no biological relationship?
Put that to your DH and see if he can give you an answer?

Indonesia all sound rather Jeremy Kyle doesn't it.

Several options:

1. Scale back the party to just you 3 and grandparents only
2. Invite the BIL and children only and tell him none of his "partners" past or present are welcome
3. Tell BIL the party is cancelled
4. Tell your DH to grow a pair
5. Buy your profligate BIL a big pack of condoms and a biology book about how babies are made for Christmas

Birthday or Christmas, whatever is closer, get your BIL some bloody condoms ffs.

Happy Birthday to your baby op, I hope it goes well.

I think the update makes it worse. Welcome to the world of your husband putting his brothers feelings before your child’s wellbeing, never mind an utter disregard for your wishes to simply enjoy something as basic as a child’s birthday. But no, let’s all pussyfoot around the immoral adults who can’t keep their pants on or their hands to themselves. Buckle up OP, this is your life now and this nonsense will rear its head at every family occasion.

Fucking hell.

I would say plainly to your BIL that you do not want your child's first birthday party to be hijacked by his partner who clearly wants some sort of showdown with the OW, and the drama of his children meeting their siblings for the first time when they were previously unaware of each other's existence.

Who gives a fuck if your BIL and his various women are upset about not being invited? Just tell them you don't want any drama, you want to enjoy your child's first birthday, so none of them are fucking invited because none of them can be trusted to behave themselves.

I wouldn't invite any of them to be honest, they sound way too 'Jeremy Kyle' with all their drama. You don't want it all kicking off at your baby's first birthday!

Don't invite any of them, and distance yourself going forward. No good is going to come of any of it, and you have your child to protect now. Your DH needs to grow a pair.

No idea why you are even entertaining a family party for your 1 year old with all that drama.

Book a night away or something and don’t invite anyone. Inviting the kids without the mums is not going to work and you know that. Your 1 year old will not give a shit about any of their cousins at the minute. Give it another year and see if anything calms down.

BiL has several children with 4 different women. He's obviously not in a stable relationship with any of them, and is, how can I put it, in need of character strengthening. I wonder why he is allowing them to dictate whether he can take his children to a party, or whether they ever even meet. Maybe it's because of the risk of being glassed?
Anyway, as your DH also seems to be short of bottle, you can tell him (BiL) that mother of the 8 year old is definitely not invited because you are not having a violent drunk in your house.
You could let him bring the mother of the twins, as you say she is nicer, although if the other one finds out ( she will) she might turn up and cause trouble anyway.
I don't think your child's birthday party is the best place to meet the twins for the first time. Better all round to make it gradual, meet them in the park or something and take it slowly. It says something that neither mother wants to allow the offspring to go with BiL alone.