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

There'll be 40-60 people there - it's not an intimate family dinner!
Obviously invite him, cannot believe it would even be a discussion!
You, and your fiancee, don't need to sit with him and have a heart to heart - just put him on a different table or at the other end of yours and crack on.

Or, if you and your finacee are keen to cause problems, don't invite anyone's partners.

Just to add - I know someone who got married and they refused to invite another family members long term partner due their age gap. (which wasn't huge anyway) The partner did go due to feeling obligated but was uncomfortable all day. Lo and behold, the marriage didn't last and the family member went round the (very small) family trying to illicit sympathy. You can probably guess whose door was very firmly shut to them and has remained shut ever since.

No problems with your sister until your fiancé came along.

Fiancé now behaving in a way that makes you choose between then. If you choose your Fiancé it will ultimately sever your relationship with your Sibling.

She will soon have you choosing between her and the rest of your family / friends.

🚩🚩🚩

Your fiancée is a shit-stirrer. Sounds like it’d suit her for your relationship with your sister (and your daughter’s relationship with her aunt) to end.

I couldn’t marry someone who would make me choose between them and my sister, especially over something pretty minor.

If the next family event is organised by your sister and she wouldn't invite your fiancee because her DH doesn't feel comfortable with her being there, how would you feel about it?

If that one comment is the worst that happened, maybe breaking the bridges over that isn't in your best interest long term

Wow, step away from this madness. Its a one day event, your Fiancé is potentially causing a family rift. What if all your family start taking sides & others don’t come?
Your Fiancé doesn’t even have to speak to the guy on the day, she presumably has other people who will occupy her time !
You, on the other hand have a lifetime of wanting your sister in your life.
Your Fiancé is being precious over one bbq event & a comment about a child who is not hers.
Sorry, this is a bridezilla problem.

Unfortunately, we don’t get to choose our family or our in-laws!

We have a SIL who is a complete pain in the arse and has caused more than a few uncomfortable arguments over the years, usually when drunk. We’re all adults, so we de-escalate where we can, have a bit of humour about it and generally ignore the drama.

I’d be more concerned about your fiancée’s apparent unwillingness to compromise. She doesn’t have to like your BIL, or even spend much time with him, but surely she can make an effort to keep things civil for your sake. Saying she’ll rethink the wedding if you don’t handle it her way feels like a pretty huge, controlling, escalation.

If your sister and family is important to you, I’d make it clear that you’re not asking your fiancée to like her dh, just to be civil and make an effort for the sake of your family. That’s not an unreasonable expectation.

I’d also be thinking very carefully about what this says about how the two of you will deal with difficult disagreements once you’re married. Will it always escalate to dramatic ultimatums.

What a fuss. Invite him.

I'm quite pleasantly surprised by this thread. The usual MN mantra is "your wedding, your choice", "go no contact", etc. @Omegaez I think that should probably tell you something.

Your fiancee had an argument. It doesn't actually matter why the DH wasn't invited. He wasn't, and he took it as a deliberate exclusion. I think most people would, or at least wonder about it, even if they weren't brave enough to say so. People generally aren't as carefree about social inclusion as they pretend to be on social media. Most people would feel the sting if they were left out of something that they would ordinarily be included in without explanation. I understand that no explanation would have been offered if it was unintentional, until the oversight was revealed, but that's small comfort to the one who has been left out.

Your fiancée needs to understand the impact of excluding your BIL from the wedding. It can't be undone. No amount of making up can undo being purposefully excluded from a key family day. Does she really want to impact your relationship with your sister like that? Is her feeling of discomfort that a man is in the room when she marries more important than the years of bad feeling this could cause?

I'm on team BIL here. I think you should be considering whether it's worth sacrificing your family relationships because your fiancée had an argument.

She did leave him out of the family BBQ, yes?

Your BIL has a point. Your fiancee didn't like him calling her on it. I think he was pretty decent apologizing for letting it get heated, but no, he shouldn't apologize for being truthful. You don't leave spouses out.

Your fiancee doesn't like him and is trying to push him out of your family group, so your BIL has a valid point. It's super rude to not invite her husband to the wedding and if I were your sister, I'd not go to your wedding and be very low contact with you and your controlling wife. You're going to lose your sister over your fiancee being a dick.

Just invite him. He is your sister s husband and if he not invited your punishing your sister and causing issues...

Exactly this. OP, your fiancée sounds horrible. Maybe she is the problem, not BIL….

Or maybe she doesn’t just play nice with him like OP does. It’s quite fortunate for him, given he also hates BIL, that the Fiancée is taking the blame for what is undoubtedly a difficult relationship between the couples.

It’s particularly malicious of nil to say what he did to a 9 year old. I would like to know what she feels about that as it isn’t okay and it is a red flag.

Is there a history between your fiancée and bil or is your fiancee good at sniffing out bad people and not able to play the long game?

The problem with this 'drama' is that if you invite just your sister and not her DH, you are effectively asking her to pick her family or her DH.

She will choose her DH.
She will also be pissed off with you for a VERY long time.......and I don't blame her, it's shitty thing to do to put her in that position.

Also want to echo what pp have said about having concerns over your fiancé and what's she said about not having a wedding if he's there. Huge 🚩. Saying something like that is not normal at all.

You can't not invite your sister's husband

Just invite him. Humans make mistakes, these don’t sound like unforgivable things.

Why wasn't he invited to the BBQ in the first place. Your sisters DH.

I can't image having a BBQ with my sister with her partner.

Likewise I would not marry someone making me pick between them and my family for someone that seems minor

Your fiancee excluded your sister's husband from a barbecue and she was upset when he challenged it? It doesn't matter who else wasn't invited or what kind of mix up happened. Of course as a close family member he would take it personally. That is what started everything but you are quite dismissive of it.

Regarding your daughter if he said it as you have stated here then he was out of order. However, given your minimising of your fiancée's behaviour to date I would question context, wording etc.
BTW did your fiancé apologise for excluding him from the family barbecue or was it just a one way apology from him?

Just invite him. Be polite when he arrives and then ignore him for the rest of the day.

Your BIL might have seen something you don't when he told your DD she'd see her aunt less when you're married.
Your partner is threatening to not marry you if you invite your BIL to the wedding. Does that not ring alarm bells for you? She is isolating you from your family before you've even got married.

Invite him as it's etiquette wise the right thing to do. Get a bouncer/appointed strong people in your family to kick him out if he causes any fuss.

Invite him

Yes, agree with pp that perhaps he had a point. Is your fiancée controlling in your opinion OP? You know her better than anyone on here.