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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

How to deal with this situation? BIL & his kids as a result of an affair?

299 replies

jojobooh · 20/11/2025 14:41

Basically my BIL had an affair behind his long term partners back (has a son (10) & a daughter (14) with her) which resulted in twins being born who are now 5.

The kids have never met and are not aware of the existence of each other because of several reasons.

We have DC who are closer in age with the twins and have play dates often.
Our oldest DC talks and understands and is very cleaver.

DC see both lots of cousins, obviously separately and are aware that they are cousins and family etc.

Were having a Christmas party for all the kids in the family next month in our home, just abit of festive fun for the kids.

Now as the kids are not allowed to meet each other BIL wants us to host the party twice to neither of the kids miss out.
I think this is absurd.

Whilst we want all the kids to be treated fairly and equally I find this request unfair and OH is supporting BIL.

Why should we have two parties?

Moving forward I think this will be a similar trend when DC have birthday parties etc or other future family events we host.

And when DC are older they will be forced to keep this secret which I don't think is fair or right at all to swear young kids to secrecy.

I just wanted to see if I was BU about refusing to host this second party and if anyone else has been in a similar situation.

OP posts:
TheABC · 20/11/2025 17:26

You have two options:

  1. Say no, step back and stay out of the family drama.
  2. Lance the boil and invite both sets of kids. They deserve to know.

Also, your DH is a dick for going along with this behaviour and defending his brother.

Namechangerage · 20/11/2025 17:26

This reply has been deleted

Message deleted by MNHQ. Here's a link to our Talk Guidelines.

I think she said they are a cleaver 😉

If this is real. What. The. Fuck!

I’d stop all visits until BIL sorts his shit out because you don’t want to risk messing your own kids up through keeping secrets.

Namechangerage · 20/11/2025 17:27

TheABC · 20/11/2025 17:26

You have two options:

  1. Say no, step back and stay out of the family drama.
  2. Lance the boil and invite both sets of kids. They deserve to know.

Also, your DH is a dick for going along with this behaviour and defending his brother.

Lance the boil! Blame it on a scheduling “mishap” oops!

Acommonreader · 20/11/2025 17:30

jojobooh · 20/11/2025 15:16

BIL split up from his ex and is now in a casual sexual relationship with the twins mum.
The kids all live with their mothers but he does a lot of school drop offs/ pick ups and is active in all of his kids lives.

Do they live all locally? They might see each other in Tesco/ football match/ anywhere!
The whole situation is madness. Imagine the shock for the older kids to find out through friends accidentally- ‘ I saw your dad in the park with some little kids, they called him Daddy’
What the hell will he say then! He needs to sit them down and tell them asap. Stop participating in this OP.

InLoveWithAI · 20/11/2025 17:32

All the adults in this are gross.

There is no way I/my family would let one of my brothers get away with this.

You're allowing your children to be used.

I can't get my head around this at all.

diddl · 20/11/2025 17:35

He sounds an absolute shit & I'm not sure your husband sounds much better.

Not sure why got involved with the kids meeting up either.

FancyBiscuitsLevel · 20/11/2025 17:37

I do think OP this is the point you have to explain it very carefully to both your DP and your BIL- your dcs are too young to be able to be able to be trusted to keep the secret of the twins from their 10 &14 year olds cousins. They are also too young to be reasonably expected to not say they’ve had two parties to the older cousins.

So if BIL wants to keep the existence of the twins from the older cousins, he needs to make a choice now, either your dcs stop seeing the older two or they stop seeing the younger two. You can not expect your children to play with the other two groups and at no point not slip up and tell them.

Does how does your DP think the children will feel finding out from their cousins that they have siblings their dad hid from them? How well does he think that will go and does he think your kids will get the blame within the family?

BIL has to choose- one or the other set is kept from family events or all children are made aware of each other, even if they don’t meet up.

What he is doing is cruel to all children involved but as a parent you need to protect your dcs, you can’t protect your 4 DNs from your BIL and exSIL’s poor choices.

laughingnow · 20/11/2025 17:40

This all sounds rather implausible. Just saying.

WearyAuldWumman · 20/11/2025 17:40

Arlanymor · 20/11/2025 17:22

That's so sad - in his 60s - they stole time from him, they stole his sense of identity, they stole his opportunity to build closer links with loved ones.

It stinks, it really does.

Thank you. Yes. I had a very long detailed post in reply but I've deleted - don't want to derail.

Just to say that so many people were affected - my family member, his siblings, cousins from abroad who were denied access to him...and - as it turned out - his birth mother.

By the time we got the full story, we were too late - she'd died 4 yrs previously. From what we since find out, there's no doubt that she would have wanted to see him.

On my wall I have a picture of him a yr old being held by his stepmother and waving goodbye to someone. One of his siblings found the same picture among their mother's belonging.

FreeTheOakTree · 20/11/2025 17:41

Sort yourself out now. Why on earth would you go along with this?

diddl · 20/11/2025 17:41

Why doesn't BIL host his own Christmas parties for his kids?

WearyAuldWumman · 20/11/2025 17:42

Namechangerage · 20/11/2025 17:26

I think she said they are a cleaver 😉

If this is real. What. The. Fuck!

I’d stop all visits until BIL sorts his shit out because you don’t want to risk messing your own kids up through keeping secrets.

Edited

This. I've outlined my family member's situation. The older cousins who knew about it apologised to him that they'd had to do what their parents told them...

As my family member drily pointed out to me, two of the older cousins were adults at the time.

WearyAuldWumman · 20/11/2025 17:43

laughingnow · 20/11/2025 17:40

This all sounds rather implausible. Just saying.

I'd have said the same, were it not for the situation in my own family.

RightSheSaid · 20/11/2025 17:45

jojobooh · 20/11/2025 16:35

Apparently the partner he cheated on dosent want her kids to meet the twins either, I'm not really sure of the reasons.

She is understandably very angry and bitter about the whole situation and how she found out (the woman called her up out of the blue to ask when the kids were meeting).

It is very messy and BIL does need to put things right and be honest.
OH defends him to the core so it's hard to enforce/ say anything in relation to this.

OH's reasoning is "because the ex is an alcoholic my brother had the right to do what he wanted and it's her fault for making him so unhappy".

When I reason that most normal men would leave the relationship and have the courtesy and respect to tell the woman how he felt/end the relationship before getting someone else pregnant, he starts getting nasty and blaming the ex.

@jojobooh You can't defend the indefensible.

I'd ve concerned about your own Hs morals and values if he thinks any of this is okay.

You said all the kids live with their mothers. If his ex is such a terrible drunk, why would BIL allow that? If she is abusive again, why would he allow her to be the children's resident parent?

His a shit dad and he's a shit partner. If your H thinks putting you and your kids in this position is okay then he's shit as well. Unfortunately, birds of a feather flock together.

TheFormidableMrsC · 20/11/2025 17:46

If your partner has that attitude OP, you must know that this is how he is going to treat you one day. Fuck that. What a shitty pair of men.

pinkyredrose · 20/11/2025 17:46

Why are you keeping his secret for him? I can't believe you have his affair kids over knowing that his first 2 children don't know about them. They'll be so hurt when they find out.

LilacPony · 20/11/2025 17:46

This is ridiculous and I would not allow my children to be in this situation.
You absolutely cannot ask your children to keep a secret from their cousins. Even though they’re innocent and young, it’ll absolutely taint the cousin relations if they hear this news accidentally from your DC. So this is a ticking time bomb and you need to get out now and tell BIL to sort it out because he needs to be prepared for the fact your children will inevitably say something in the very near future.

washinwashoutrepeat · 20/11/2025 17:47

No way. I wouldn’t accommodate this at all. Hé should host a second party, if he wants.

but he needs to man up.

Arlanymor · 20/11/2025 17:48

WearyAuldWumman · 20/11/2025 17:40

Thank you. Yes. I had a very long detailed post in reply but I've deleted - don't want to derail.

Just to say that so many people were affected - my family member, his siblings, cousins from abroad who were denied access to him...and - as it turned out - his birth mother.

By the time we got the full story, we were too late - she'd died 4 yrs previously. From what we since find out, there's no doubt that she would have wanted to see him.

On my wall I have a picture of him a yr old being held by his stepmother and waving goodbye to someone. One of his siblings found the same picture among their mother's belonging.

I honestly don't think it is derailing - it's a really sad, true story about the consequences of people being deceitful and the danger of keeping secrets. And I think it's very relevant to how things could end up if this situation continues.

It's like dropping a stone into a pond isn't it? There is the initial deep impact, but also the ripples outwards that involve so many more people as you say.

That's so sad that it came out too late for him to meet his birthmother and for her to see him again and maybe set some ghosts to rest. That photo sounds so bittersweet - talk about a 'picture' painting a thousand words.

I honestly find it astonishing that people don't consider the considerable impact of betrayal - what it does to a person, how it affects their sense of self, their ability to trust others. It's a genuine act of cruelty.

AgnesX · 20/11/2025 17:50

What a shit show. Can't he (and your DH) see how this will turn out. It's like a story line in EastEnders

InterestedDad37 · 20/11/2025 17:51

No adult should ask a child to lie or conceal the truth on their behalf (except in games, obvs). This applies to your BiL, you, and all the adults concerned. But it's primarily his mess, and up to him to deal with.

waterrat · 20/11/2025 17:51

The best thing you can possibly do here is encourage the BIL to stop the lies right now.

If you can be supportive and helpful in doing that you will start to at least reduce marginally the major trauma these kids will have when they find out (which they will) that their ENTIRE FAMILY has been lying to them for years.

pinkyredrose · 20/11/2025 17:51

OH's reasoning is "because the ex is an alcoholic my brother had the right to do what he wanted and it's her fault for making him so unhappy".

Your OH sounds like a right dick. This is a similar line that he'll use on you if he ever cheats on you.

WearyAuldWumman · 20/11/2025 17:52

@jojobooh Families in this kind of situation get into the habit of keeping secrets.

i can't give you much more detail because part of it would be outing someone else and it's not my story to tell.

However, as I've detailed above it causes so much heartache. At least by the time I had a funeral to arrange, the secrets were mostly out in the open - even so, it affected the content of the eulogy and the way that things were worded.

Yes, the eulogy told the truth - and those affected knew about it by then - but the next generation was very badly affected by the fact that they didn't find out until they were adults and some of them had difficulty accepting their blood relatives.

Theunamedcat · 20/11/2025 17:53

ADogAndHisTed · 20/11/2025 14:44

Twins eh?

Yup 😂