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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Sister ruined Christmas with stupid affair drama - AIBU to be really stressed?

243 replies

aerisgainsborough · 09/01/2026 13:32

It’s a long one, grab a brew and a biscuit.

I’m 36, sister B is 33, sister C is 31. All married, I have 3 children, we’re close knit, live within 5 miles of each other and do stuff with each other and our parents all the time. Middle sis has always had issues with self-esteem and either hates herself or loves herself. Has always been impulsive and attention-seeking (my youngest sis and I think she may have BPD).

B’s husband is a bit of a wet lettuce and very surface-level, is a bit ignorant and only speaks to my kids to tell them off in a really patronising voice.B He has “not made his mind up” on whether or not to start a family so B is kind of stuck in limbo on that and they won’t discuss it. She tries to let on that she doesn’t want children, but it directly contradicts what’s she’s said before and she flip flops constantly. They have very few commitments, a cat and a weekly board game club, and sit playing online games all weekend and that’s about it but reckon they live busy lives.

However, B cheated on him 10-ish years ago and he forgave her, which made us all lose respect for both B and for him because she really was horrible to him. He then proposed and they’ve been married for 5 years. He struggles a lot with anxiety etc and she says she feels more like his carer, but we’ve never seen any behaviour to support this so just generally have to take her word for it.

Recently B started a new job (she changes jobs nearly every year) and has got friendly with a male co-worker who is 10 years younger and they’ve started up a fling, despite them both being married. She “left” her husband almost immediately and declared her love for him. He strung her along for weeks, saying he couldn’t leave his girlfriend yet, going through phases of constant messaging and then ghosting her. Eventually she confronted this lad and said she loves him and he’s told her he regrets it all and nothing can happen. I was sworn to secrecy during all of this and nobody else knew but me, which was horrible and during Christmas week so I spent the whole Christmas period hosting the rest of the family while B and her husband went and played happy families with his side. I’m autistic and had a very intense internal struggle with all this. I was crying, feeling sick, unable to think about anything else. I was trying to cope with everything changing, her betrayal and not being the person I thought she was, them already being split up but not telling anyone, When it finally all came out and she told everyone, they were all angry at her for putting me in that position. It’s all everyone has been able to talk about since and my mum keeps trying to get me to find things out. I’m the eldest default child who gets leaned on by everyone and I’m just so tired.

So B is now just living with her husband as housemates and helping each other set up dating profiles. She is meeting up with a 40-odd year old she met on a kink app and during a phone call he told her that he had massive hands and could choke the life out of her if he wanted to. I’m sitting there listening as she tells me she’s meeting up with him at his flat in Manchester and I am now picturing her being chopped up and dumped in a bin. I’m trying to put some distance between me and her problems because we all get a bit enmeshed at times and it’s not good for my mental health but I am worried sick that something will happen to her.

My parents fully believe that B and husband will get back together and don’t know about B being “on the apps”. I’m sick of them asking about it and just don’t know what to do about it all. Thank you, if you’ve read this far.

OP posts:
aerisgainsborough · 09/01/2026 14:08

SandrenaIsMyBloodType · 09/01/2026 13:59

People who don’t understand autism often suppose that it makes you unemotional. The opposite can often be true, especially for women. Kindly, your neurodivergence means that you are particularly ill-equipped to deal with this. You probably have an over-developed sense of what is right and wrong and it is unfair of any member of your family to try to draw you into drama and secrets. It is bound to make you feel constantly anxious.

You can’t control your sister’s behaviour anymore than you can control your emotional responses to it. You can, however, protect yourself by being clear about your boundaries. Experiment to find a phrase that feels authentic to you and shut down conversations that make you anxious and are essentially about things that are nothing to do with you; something like “I just cannot talk about this any more. It really upsets me and I need you to leave me out of it”. If they don’t yet understand how your autism is linked to your anxiety then it’s about time they learned. (Eldest daughter and mum to 2 DDs with AuDHD and an autistic DH).

Thank you for seeing me. Me and two of my children have autism and you’ve described it perfectly. I am empathetic to the point of pain sometimes and I didn’t think of the social justice angle. I get taken advantage of because of it by people who need someone to listen.

OP posts:
CorvusPurpureus · 09/01/2026 14:08

If you were B, I'd be advising you to focus on extricating yourself from your miserable marriage (it sounds like they're doing that, & amicably, which is great). Then staying away from dating for a bit (she's obviously got appalling judgement in this area & needs to work on her self esteem, rather than throwing herself at an attached colleague barely out of his teens, followed by Mr Kinky Strangler Hands).

But...you are NOT B. She's a grown woman. She doesn't need her big sister's input into her private life. In fact, it's probably doing her no favours at all - she needs to start seeing herself as an autonomous adult, not the ditzy troublesome middle sister like she's still a teenager.

You should back right off. Tell the rest of the family you aren't getting involved & they should ask her directly if they want to know what's going on. Tell B you don't agree with some of the stuff she's doing, you'd rather not hear about it, but you're there for a coffee.

Basically - not your 🎪 not your 🐒 🐒.

Icouldwriteabookonmydisastrouslife · 09/01/2026 14:08

I have no advice but I think some posters are being harsh considering you’re ND . Please have a bit of empathy for OP . My family are all ND , we don’t always see the world like other people and we can’t understand it as quickly as others.

💐 Hope you’re ok . Maybe take a step back and rebalance your brain for a bit , tell her you care but you can’t be there for her right now . You need to concentrate on your own wellbeing,

Noslogans · 09/01/2026 14:10

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aerisgainsborough · 09/01/2026 14:11

Cantheowneroftheredcorsapleasemovetheircar · 09/01/2026 13:37

To answer the question - yes, you're being unreasonable to be stressed.

This is their drama. Why is it bothering you so much??

People love all sorts of lives.

As for not being the person you thought she was - you knew she was a cheater? She did it 10 years ago?

All of it, including your emotional investment in your sister's marriage, is a bit weird.

It’s the games she plays of pretending to be so principled and she criticises my parenting, pretends she has the perfect marriage, and only gets in touch when she wants something. It’s made us all realise that she hasn’t changed at all and I feel very sorry for my brother in law. Yeah he’s a bit of a wanker but nobody deserves that.

OP posts:
Noslogans · 09/01/2026 14:12

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aerisgainsborough · 09/01/2026 14:12

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Late diagnosed autism means I mask exceptionally well.

OP posts:
FlapperFlamingo · 09/01/2026 14:12

You're way over-invested and over-thinking about her life. You need to back off massively. If she calls you just tell her "sorry, I don't want to know!". If she goes silent - then great because she'll leave you alone. You honestly need to develop your own friend network and probably move away from being so close to family. You all sound a bunch of drama llamas.

Noslogans · 09/01/2026 14:12

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Primaris · 09/01/2026 14:13

Don’t agree to be sworn to secrecy.
It may help to make that a condition of her telling you anything.

Even if you are a mental health professional, you are not her therapist. You cannot be a substitute therapist for her either. If she needs to talk she has other options - therapy, the confessional, pastoral supports, the Samaritans etc.

I’m being very blunt, not to be unkind, but hopefully to help define where the lines are.

StoppingByWoodsOnAColdEvening · 09/01/2026 14:13

Icouldwriteabookonmydisastrouslife · 09/01/2026 14:08

I have no advice but I think some posters are being harsh considering you’re ND . Please have a bit of empathy for OP . My family are all ND , we don’t always see the world like other people and we can’t understand it as quickly as others.

💐 Hope you’re ok . Maybe take a step back and rebalance your brain for a bit , tell her you care but you can’t be there for her right now . You need to concentrate on your own wellbeing,

Then the OP needs to work as a matter of importance on developing extra-strong boundaries, if she has an enmeshed, oversharing family who make a meal out of any one member's activities, and being told about a sibling's affair made her cry and feel sick and unable to think about anything else throughout Christmas (despite the fact that she neither liked her sister's ex-DH nor thought it was a healthy relationship).

Whether or not she is ND has no bearing on her ability to change other people's behaviour, but may make it extra important she develops a way of removing herself from the situation if she can't cope with it.

Noslogans · 09/01/2026 14:14

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aerisgainsborough · 09/01/2026 14:14

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Yep. I masked while my family were around and after a really fake and horrible Facetime with B, it got too much and when my husband saw me upset when everyone had gone, I told him. He was upset that she’d put me in that position and telling him helped a lot.

OP posts:
ZoggyStirdust · 09/01/2026 14:15

You’re unreasonable to lose respect for Bs husband for him being cheated on. He was the victim (twice)

aerisgainsborough · 09/01/2026 14:16

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I did have some occasional time alone and everything welled up and I then had to contain it all and put the happy host face on again. Not being able to face my feelings and talk and deal with it made it a lot worse.

OP posts:
aerisgainsborough · 09/01/2026 14:17

ZoggyStirdust · 09/01/2026 14:15

You’re unreasonable to lose respect for Bs husband for him being cheated on. He was the victim (twice)

I lost respect for him not having some pride in himself and running in the opposite direction. He begged her to take him back even though she was in the wrong, she played mind games with him and it was very sad to watch.

OP posts:
Noslogans · 09/01/2026 14:18

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aerisgainsborough · 09/01/2026 14:19

Primaris · 09/01/2026 14:13

Don’t agree to be sworn to secrecy.
It may help to make that a condition of her telling you anything.

Even if you are a mental health professional, you are not her therapist. You cannot be a substitute therapist for her either. If she needs to talk she has other options - therapy, the confessional, pastoral supports, the Samaritans etc.

I’m being very blunt, not to be unkind, but hopefully to help define where the lines are.

I’ve been suggesting to her to get private therapy or even marriage counselling so that they can discuss things with someone who doesn’t know them. I’ve pointed her in the direction of the BACP register, Counselling Directory etc

OP posts:
Noslogans · 09/01/2026 14:19

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aerisgainsborough · 09/01/2026 14:22

Also I was quite overstimulated all of the Christmas week and the week either side because there were people coming round, Christmas dinner to plan and cook for 10 people, social family occasions to attend, neurodivergent/disabled kids to tend to and make sure they weren’t getting overstimulated. Supporting my mum through her sudden redundancy, parts of my dissertation to write, clients to see. I’m already going into all this at quite a low ebb so yes, it affected me greatly. The being made to keep it a secret part was what I struggled with the most.

OP posts:
aerisgainsborough · 09/01/2026 14:24

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My husband helped out loads when he wasn’t switching places with me to look after the children. A lot of people, a lot to do.

OP posts:
ohyesido · 09/01/2026 14:26

It sounds like you want to complain about B and have everyone agree that she’s a bad sister. Why would you feel sick and stressed about her affair?

aerisgainsborough · 09/01/2026 14:30

FlapperFlamingo · 09/01/2026 14:12

You're way over-invested and over-thinking about her life. You need to back off massively. If she calls you just tell her "sorry, I don't want to know!". If she goes silent - then great because she'll leave you alone. You honestly need to develop your own friend network and probably move away from being so close to family. You all sound a bunch of drama llamas.

We’re actually not drama llamas, with the exception of my mum and B. I love the times when it’s just us, I get to enjoy my children and husband and just be in each other’s company. I also have a few brilliant friends that I see nearly every week, are also ND and we are supportive of each other.

OP posts:
Keroppi · 09/01/2026 14:30

If she comes to you for advice just give slow replies and boring answers
Don't pick up her calls
You need to be less available
Perhaps you need some stock replies

"That sounds hard. I hope it works out for you xx I'm just heading out now, chat soon, bye"
"So sorry but nows not the best time, I'm just out/busy/dealing with some work/kid stuff, catch up another day, love you"
"Awww yeah, sounds tricky. I know that you'll come through it though as you're strong. What are you getting mum and dad for birthday/total subject change"

JoshLymanSwagger · 09/01/2026 14:31

@aerisgainsborough In the kindest possible way I'd like to suggest you block your sister B.
Or at very least mute her and see if your DH could check all her messages etc to you each evening to filter all the crap/angst she is causing.
You didn't want to get involved, so send one last message telling her you simply don't want to know.
Let her sort out her own messy life.
💐

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