To tell my sister she can’t bring her husband to my wedding?

Your BIL is a d1ck, but he's your sisters husband and if you want to have a relationship with your sister and not cause anymore drama, then he needs to come.
Your fiancee sounds very controlling. If she's threatening to call off the wedding over this, then she really can't love you as much as she says she does. Sorry, but true.
I know it can be hard to be assertive, but you need to put on your big girl pants and tell them all they are acting like primary school kids.

Yes I find the best way to manage in law relationships is to leave DH to deal with his side and I deal with mine. And we never blame the other for a decision that they don’t like.

by getting married you are pulling into your orbit a whole load of people you may not like but your spouse loves so you get on with it. Just try not to get too involved

Actually I think you explained everything fully and accurately. What you are now doing is backtracking/egging the pudding to fit your fiancees narrative, probably because you were not expecting your fiancee to get such a negtive response. To say that she might not marry you if you don't go along with her wish not to invite him, despite the obvious family fallout for you, is manipulative and pretty nasty. I can understand if he had done something terrible - remember someone refusing to go ahead with their wedding if fiance insisted on including his convicted sex-offender uncle - but this is different. People argue and say stupid things. Don't wait until you have joint children and she's weaponsing them to sort this out.

He was horrible to call her a controlling bitch, but I don't think she's being very nice to you by saying that's enough to not want to get married if he's there. How are you going to go forward if you have to make this choice every time family come together?

But it's also not that nice of your sister to refuse to come without him, she's making you choose just as much as your fiancee is.... but is he going to give her a hard time if she does?

To be honest, if my own sister didn't invite my husband to her wedding, I likely wouldnt attend and I probably would keep significant distance from her afterwards too.

Every family had arguments and tiffs, and even some members of the family you dont particularly like, but if I knew my husband was intentionally left out because they "didnt like him", I would be furious.

Whilst I understand there was a misunderstanding about the BBQ, that he straight away jumped to it being your fiancé that was excluding him and accusations of her being controlling (unpleasantly phrased, but on the evidence here, accurate), points to there being some tension between fiance and bil before this. Otherwise it's an extraordinary conclusion to come to.

So what happened before the bbq to give the bil this impression?

Invite him. The more you explain, the more I am leaning toward your fiancée being more of an issue.

Getting married and being in a relationship is about compromise. I understand why your fiancé doesn't like him but by not inviting him, it's punishing your sister and to some extent it is punishing you as you are agonising over this and will be the one to suffer the brunt of the fallout. I think your fiancé needs to stop with the ultimatums and think about your feelings and what not inviting him means for you and your family in the future. The day is about you two celebrating your love for one another amongst family and friends. Your happiness is about your love and commitment towards eachother, guests are just in the background and hopefully easily ignored if needs be. I had to invite a couple of people I didn't like to my wedding and it was fine. Didn't detract from the day at all.

Word of warning from someone who did exclude a close family member from my wedding. Be prepared for huge ramifications and effects that go far beyond the wedding day, even when the uninviting is entirely justified. In my case, my sister was incredibly unpleasant, nasty to my friends and finished off by announcing she ‘wished I was dead’ at my hen do. Then never apologised. This is a fully grown woman with a family of her own, and a history for ruining things for me. I justifiably rescinded her invitation but it resulted in my dad refusing to come to my wedding, my mum almost not coming (though she thankfully did in the end) and a fracture in the family I don’t know that we’ll ever fix. I wanted to protect my wedding from drama - and I did, we had the most amazing day - but that came at a huge cost. Be really sure that the potential cost of excluding your brother in law is worth it.

I think you should say to your fiancee that you need to invite BIL because clearly your sister is in a difficult position and you don't want her isolated incase she needs both of you to help if her relationship goes south.

Interestingly, I feel the same about you keeping your sister on side in case your relationship goes south. But that's just Spidey senses, and no one wants to know about those....

I think unless there was violence, threat of violence or other specifically nasty and abusive behaviour, you should invite him. If you don't, that is a permanent family rift that may never heal.

It seems as if you would invite him if the only falling out had been the bbq row? You are hesitant because of the comment to your daughter but it is not down to your fiancée to decide whether that was totally out of order. It was probably not his place to make that comment but you should address it, not her, and I don't think it warrants destroying your relationship with your sister. He does sound a bit of an arsehole and your fiancée does seem a bit controlling, tell them both to grow up.

Hang on...

Your sister was invited, so why didn't she message/text and ask if her DH was included?

That would be the most obvious thing to do.

At the mo - in your shoes - either call it off or elope.

I couldn't be arsed with the stress and he said/she said crap the your OH and your sisters DH are pulling.

They sound like they have an average age and intellect below that of your own daughter.

Having read all your posts, I don't understand how this ridiculous spat between your fiancee and BiL is such a massive issue that your fiancee would threaten not to marry you over. Seriously, she needs to get a bit of perspective. She's not being asked to marry the BiL, neither are you asking her to include him in the wedding party, but just to have him invited as a guest like the rest of your family (which he is). I think you need to be a bit more assertive, be the sane voice of reason (and the bigger person) and tell your fiancee that whatever happened in the past is just that and you are not going to allow it to jeopardise your future with her. If she insists that it's a dealbreaker, then if I were you, I'd be reconsidering the marriage!

I doubt the comments about your fiancée being controlling came out of nowhere...
Sounds like she loves the drama. Did she apologize for calling him an asshole?

Invite him, you’ll both be too busy to notice him on the day. He may hate it that you’ve invited him as it removes any reason to moan about you more. Be the bigger person/people- the ball is now in his court to behave front of the whole wider family- if he’s a dick on the day they’ll all witness it. If he’s ok on the day job done, you hopefully won’t need to invite him anywhere so important or poignant again

I see your point especially speaking to your child like that and it’s your day, but I think you’ll have to invite him or it will cause a huge scene.

This is where family celebrations are not like what you see on tv (unless Eastenders)! They’re not all polished and well presented, there’s feuds and backstories a plenty. If you do invite him ensure they’re sat furthest away from you and plenty of photos with just immediate family / parents and siblings… tell the photographer clearly before hand.

Have you asked your fiancée how she will feel if she’s excluded from future family events arranged by your sister and would she expect you and your daughter to also turn down the invite? Because that’s where this is heading

Oh dear, they sound as bad as eachother. Be careful OP, looks like you’re marrying someone who’s not going to have a positive impact on your life.

Does your DD have a good relationship with your partner?

I think you are in a difficult position. Of course, you don’t want your fiancé to be miserable on your wedding day. But equally, not inviting your BIL is highly likely to far-reaching consequences for your relationship with your sister.

Firstly, this sounds like a argument which was not all of your BIL’s fault- you admit that communication was poor, for instance- and it sounds as though it is possible your fiancée may not be quite as faultless as she would like to make out. And he has apologised for letting it get heated, even if the apology is not suitably grovelling for your fiancée (though she could be being unreasonable on that front too). Has she apologised for the poor communication? In any case, it does seem rather a significant over-reaction to ban him from the wedding on the basis of what seems like a relatively minor argument. There is being stubborn and having boundaries, and then there is being pig-headed and selfish. If I’m honest, I think your fiancée might be in the second category, unless something more serious has occurred that you have not mentioned.

I’d also suggest that if this situation is enough for her to call off the wedding, I think you have bigger problems in your relationship. She must realise that this is your day too- how likely is it that you are going to fully enjoy your day, knowing you’ve thrown a grenade into your hither to close relationship with your sister? Yet she is still insisting on this course of action. This is not reasonable, in my view, unless there is more to this argument than has been discussed so far.

Not inviting your BIL is likely to cause a significant rift with your sister. Are you prepared for that? Whatever the reason, you are forcing her to chose between you and her husband. You will likely lose. It will be a very hard rift to heal. Are you willing to be estranged from her and not play a big part in her life over this argument? Family gatherings are going to become awkward, family picking sides (and many will), possible resentment from your family for creating this issue unnecessarily, and losing your close relationship with your sister. what if they have children- you aren’t going to be allowed to be close to your niece/nephew if you have a poor relationship with your sister and an antagonistic relationship with their father. Are you willing to head down that route, over a stupid argument, for which an apology has been made. This goes beyond your BIL not being your cup of tea- or even a bit of an idiot- this is actively excluding your brother in law from a family event. You need to be realistic about the outcome of that choice.

When it comes to your relationship with your fiancée, this situation would be waving big red flags to me. Of course, I’d be willing to take a stand against my family/risk a rift with a sibling over something very serious. But the argument, as you’ve outlined it, is not something I would burn down my relationship with my sister over.

And I’d be unimpressed that my fiancé is willingly putting me in that position over what ultimately appears to be something relatively minor. It comes across as manipulative of her to threaten to call off the wedding in order to force your hand. Unless there is more to it, I’d have a hard think about your relationship and your fiancée ‘s behaviour towards you and others, as well as what your relationship with your sister means to you.

Absolutely this!
I think that there's possibly a lot more to this than has been divulged.
Do NOT let your fiancée alienate you from the family.
I wonder what has made the brother in law react like this, what has been said before? Calling her a bitch is disgusting, but you said it was both sides, what did she call him?
Another poster also mentioned that your sister was sent an invitation to the BBQ. That, to me, would count as an invite, unless it specifically left him out?
I don't know, this all seems a bit odd to me.
It also seems like you are afraid of standing up to your fiancée and are making excuses for her.
It was wrong of your brother-in-law to involve your child, but actually, what did he mean by this? It doesn't automatically sound sinister.
What will be more damaging for your child, is to have her wider family and support system fractured and watching warring grown ups rowing and swearing at eachother.
See the wider picture and tell your fiancée that he's coming, she doesn't have to speak to him and that you are not willing to risk your entire family falling out over this. See what she says, if the wedding is cancelled or a huge fuss is made, then I suggest you look carefully at who the problem is here.
I thought a poster, who mentioned a similar scenario with her own family, spoke a lot of sense. Ban him only if you are willing to risk them all saying that they won't come!

I agree with this. And family may feel they have to start picking sides- so you may find yourselves excluded from other family events, especially if your family feel your fiancée is the instigator of the problem (or at least allowing it morphe into something it did not need to become). It is definitely going to make life awkward for you and your family.

Nothing about the argument you have outlined is significant enough for you to throw a grenade into your relationship with your sister for, in my opinion.

As I said, I think your fiancée is being a bit OTT and quite manipulative. Are you going to be able to fully enjoy your wedding day, knowing you’ve caused a rift in your family? She seems rather unconcerned about that. You seem far more considerate of her feelings and point of view than she is of yours. That might be something to think on.

BTW- I’m not saying your BIL behaved well. He didn’t, he sounds insecure and a bit of an idiot. He should not have sworn at her and called her names (though she sounds like she was just as bad in response), and he should not have included your daughter in it in any way. Though I think that should more be between you and him, than anyone. I just think your fiancée is not a 100% innocent party in all of this, and she is choosing to put you in a difficult position over something relatively minor and for which an apology has already been proferred.

But I wonder why he would think your fiancé would exclude him? Is it all his insecurities or is there something about the way your fiancée behaves towards him/more generally that made him jump to that conclusion?

I agree.

Obviously calling her a "bitch" was very rude, but it is interesting that he chose "controlling" as the adjective here. I wonder very much if there is more of a back story here that the OP is keeping quiet about. Has there been other tiffs or tension apart from the BBQ and comments to your DD.

The fact that the fiancee is now trying to get her own way by threatening to pull out of the wedding if he is invited lends even more weight to the theory she is being controlling

This was an argument between him and her. Two people. You can leave it at that OP.

Or you can get involved. Make it an argument about 3 people, block him from your wedding and then your sister will join the argument. That's 4 people. Your mum and other family members will have their opinions and take sides, that's your while family involved now.

Do the right thing. Refuse to get involved and let this stop at 2 people.