BIL wants my husband and his abusive ex to sit together at the wedding

What a load of biased codswallop. You have no idea of the circumstances under which he left his family. OP said his ex was abusive, and that DB and SiL refused to even listen to his side of the story before making their minds up to support his ex. What was he supposed to do - stay in an abusive marriage for the sake of the children, who would then grow up in a toxic atmosphere.

And he hasn’t ‘abandoned’ his children - sounds like shared custody. Sounds to me as though you can’t accept that women can be abusive. Telling OP to watch out for herself is pathetic - do you not think she knows her own husband and the situation they’re in. Just because he’s a man doesn’t automatically make it all his fault.

If "He doesn't attend. I don't love this as it plays into their hands and he is the bad guy with the girls."

If it wasn't for his DD, and them repeating the line "why won't you sit next to money" I think not attending would work and would be brought up for years to come.

Is there anyone they both trust who could mediate without weighing in?

Would there be any chance of DH talking to BIL again in person in a way where he lays out the options which are still workable but do not involve sitting next to the Ex. And without anger between them could ask BIL why these options don't work. And also find out who requested this...(its the ex) And also try asking BIL how he would feel if DH tried to do something like this to him.

If he's calmly provided a list of options and BIL turns down every one, that would be the stage to ask why BIL is insisting and to offer to withdraw as best man or even the event. But as an offer, not a threat.

If do it for your children is brought up, he could say I am doing it for my children. All my children.

I'm sorry OP this is a really annoying situation for you both

If i was your DH I'd consider either

1. Resigning as best man....being a regular guest.

1. He says "do you know what its your big day... fine" then you arrange to have to girls there and then there is an illness/ emergency on the day so he and you dont attend (something really plausible so he is the "victim") this stoops to exs level though.

1. He doesnt attend. I dont love this as it plays into their hands and he is the bad guy with the girls.

He shouldn’t go , you shouldn’t go . Don’t play the games. Mumsnet hates step parents , so the people saying DH is the abusive one etc are saying it because of that-don’t rise to it . First wives tend to be revered/ always right etc .

If he is the abuser, why is the ex cheerfully wanting to sit next to him? I would miss a wedding like this than sit next to my abusive ex.....which oddly enough the OPs DH is considering.

Why is it that you assume that the woman must be the victim? Men get abused too you know. And its people like you that make them not want to open up about it. You should take a long hard look at yourself and your prejudice.

Possibly because he realises that it’s designed to be a snub to OP and their child. Ex gets to sit next to DH and their daughters and play happy families, while OP is sitting alone with their son. They would be sitting apart anyway as DH is best man but this seems to have been planned to make the reception as awkward as possible.

Given the update about his ex needlessly involving their young daughters, it’s my guess that ex has specifically asked to sit next to DH. If - as some posters are suggesting - he was actually the abusive one, why would that be ? And why on earth would the bride and groom try to facilitate that to the point of DH and his brother falling out ? It’s their wedding, and given the history between DH and his ex I would have thought seating them at the same table was risky enough, never mind putting them right next to each other.

There’s something off about this. If OP’s characterisation of ex is accurate, and the request has come from her, l would be questioning her motives, given the potential for trouble.

Would you stay in a marriage with an abusive partner ? What good would that do the children ? And why do you think OP’s DH is the abusive one ?

If they disapproved of his behaviour why is he still in the family as best man but they are taking it out on his new wife though? He’s the one who left his children.

@GotTheBluePeterBadge that is so manipulative. Those poor girls. Your BIL must have very little respect for the welfare of his nieces to allow the discussion to be relayed to them.
Ideally your husband should contact his brother, tell him he is not going to allow his daughters to be used as a pawn in whatever game is being played and withdraw completely from the wedding.
I would be so angry that at a minimum, 3 adults are using 2 young girls in their game playing.
In your case I would have nothing more to do with them .

The daughters are still very young and you already have a child with their father.
That means he left his wife with very very young children and explains why his brother and SIL took her side.

I'm leaning her way myself at this point.
I don't think much of any man who abandons young children.
The abusive partner may be the one you hitched up with.
Watch out for yourself as it could be a pattern of behaviour.

Absolutely unacceptable to have dragged the girls into this. I agree with the PP who thought this may be the ex W manipulation the SIL in a "wouldn't it be nice if ..." scenario.

Your poor DH

But the bride looks to be driving an agenda. Using her own wedding. Even if you’re on board with the whole performative farce of wedding venues, bridesmaids and top tables bollocks when people have been together for years, sitting this bridesmaid next to this best man is next level goading. It’s pretty unhealthy to carry that sort of bitterness for years, whatever the original resentments. So her siding with the ex is potentially indicative that they share similar personality traits.

Fair enough I’ m just saying when a woman says she has been mistreated we believe her until proof of the contrary I think we should afford the same consideration to men in the spirit of equality.

Probably, if there was clear indication that there was more to the story, as there is here.

For the record I voted YANBU I’m just saying that it would be different if there was more to the back story.

Indeed. Was ever thus on here with some posters.

Would you be asking for the man’s side if roles were reversed?

I’m just saying I wonder the woman’s side of the story is given that both the bride and groom side with the woman in the scenario.

The sister of a friend of mine was getting married and they wanted to invite her abusive ex husband, the same ex husband that had beaten not only her but their daughter too. It was batshit, their reasoning...he hadn't done anything to them

Safe to say my friend just said it's me or him, they thought she was being difficult but he wasn't invited. Can't imagine doing something like that to your own sibling

Just support your husband OP, it's all you can do

If it was a woman saying she’d been abused by her ex and showing her new DH mails and other proof of it would you doubt her?

I didn’t miss that nuance. I’m not sure why it’s relevant how she met the bride if they are now close friends. It sounds like she’s closer to the bride than the groom is to his brother anyway.

All I’m saying is the fact that both the bride and groom side with the Ex feels like there’s more of a backstory.

OP’s DH could just not be best man if he has an issue with it but I can see why the groom would be upset by that. I would probably just suck it up for the sake of the couple. Obviously if the abuse was significant that would be a different story.

Indeed

All of this.