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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:
Skybluepinky · 09/01/2026 15:55

Not your circus not your monkeys, just tell her you don’t want to hear about it.

outerspacepotato · 09/01/2026 15:57

I disagree. Boundaries are easy.

No.

What are you afraid will happen if you shut her down?

Setting yourself on fire to keep your sister and her husband warm is extremely unhealthy. If you have difficulty saying no to things that harm you, you need therapy yourself. You can't fix her. You also can't act as her therapist or sounding board or any of that.

Think of it this way. When you participate in this toxicity, you are taking away a healthy you from your own husband and children.

godmum56 · 09/01/2026 15:58

aerisgainsborough · 09/01/2026 14:03

Everything I have learned about my sister’s marriage this past few weeks has been against my will. She told me all of this and even when I told her it made me uncomfortable, she insisted on “getting it off her chest” because “it was killing her”. I work in mental health and it means I get taken advantage of sometimes because I’m kind and want to help.

I’m not really keen on her lifestyle because they’ve never grown up past about 20 and I don’t want to hear about her being tired from staying up gaming online when I spent half the night on the floor next to my disabled son’s bed because his melatonin hasn’t kicked in.

"I work in mental health and it means I get taken advantage of sometimes because I’m kind and want to help."

If you don't develop switch off mechanisms, you won't make it to retirement. Say clearly and firmly "I will not listen to this" and mean it. You work in mental health, you know that the only person who can make a difference to your sister is your sister. If you are any kind of competent clinician, you know what to do, you just have to do it. So yeah YABU.
edit: You learned stuff from your sister against your will? Did she have a gun or something?

InWithPeaceOutWithStress · 09/01/2026 16:00

Your sister is venting to you. It’s often what loved ones do with one another. I think you should work on compassion and being less judgemental. You have a solid marriage and children whilst your sister appears to be struggling to achieve that due to low self esteem.

InLoveWithAI · 09/01/2026 16:11

So you're autistic, but you think your sister has BPD? Why do you think it's BPD (an awful and quite rightly, now contested diagnosis) and not autism?

Your post is really judgy.

333FionaG · 09/01/2026 16:26

Let your sister live her life and make mistakes. Tell her you don't want to know when she starts oversharing. Be firm with her, Focus on your own marriage and children. Tell the rest of the family that you are not interested in looking out for, or looking after, sister B, she's an adult woman with capacity,

aerisgainsborough · 09/01/2026 16:27

BellesAndGraces · 09/01/2026 15:45

Kindly, you can’t see the consequences of your own actions and you’re older than her! You are refusing to accept the role that you are playing in this by allowing yourself to be so overly involved in her life. You have a choice and can step back if you choose to.

If it helps, practice phrases you can use to stop yourself getting drawn in.

She’s messaged me this afternoon and was asking advice about this date she’s going on so I’ve said as long as you’re safe and send me a drop pin and let me know you’re home safe, I don’t want to hear any more. I feel guilty and like a shit sister but I don’t want to be drawn in. It’s not helping either of us.

OP posts:
TFImBackIn · 09/01/2026 16:28

I would be absolutely terrified if my sister was planning to meet a man who said something like that. I'd do anything to stop her from going there.

I think in future you need to say that no, she can't speak to you in confidence. She can't ask you to keep a secret. It's not fair on you. If she tells you anything it should be in the full realisation that you will tell at the very least your husband.

Sassylovesbooks · 09/01/2026 16:29

You need to take a massive step back. You are not responsible for your sister's life or the choices she makes (even if they are poor ones).

As for your parents, tell them the truth regarding your sister - her and her husband are living together as housemates, as far as you can see they won't be getting back together, and your sister is using dating apps. Don't protect her. It's not your job to protect her from your parents disapproval.

Make it plain to your sister that you don't want to know details. Tell your parents/other siblings to ask your sister themselves if they want updates.

Concentrate on your own life, and your own family. Your sister is an adult. Yes, you can advise her, but ultimately how she lives her life is down to her, not you.

Boomer55 · 09/01/2026 16:32

Not your drama, not your problem. 👍

aerisgainsborough · 09/01/2026 16:32

InLoveWithAI · 09/01/2026 16:11

So you're autistic, but you think your sister has BPD? Why do you think it's BPD (an awful and quite rightly, now contested diagnosis) and not autism?

Your post is really judgy.

She’s not neurodivergent and she’s even said herself that she might have BPD in the past. She struggles with impulsiveness, fear of abandonment, aggression, no sense of self outside of a relationship, patterns of unstable relationships and splitting. As part of my training as a MHP, I learned a lot about it but I don’t diagnose people. Is it not an accepted diagnosis anymore, similar to Asperger’s not being diagnosed separately anymore because it’s archaic? What does current research offer as an alternative diagnosis for these patterns of behaviour?

OP posts:
Uhghg · 09/01/2026 16:33

It’s really difficult when it’s your own family members because you are of course going to feel worried for them.

But you need to physically create some distance from her.
Say you’re busy, don’t meet up or answer the phone as much.
Tell her you don’t want to hear it when she starts.

She sounds awful - having an affair twice.
But this is not your life and you do not have the mental energy to spend it on her as well as yourself, DH and kids.

I have a rule that I do not (try not) to have other people making me feel stressed out.
As a single parent my energy needs to go on myself and DC.
Life can be hard enough without adding other people’s drama to the mix.
This attitude came after years of being dragged into my parents and siblings dramas and I used to spend more time and energy on their relationships and problems than my own,

You cannot control what other people do.
If they want to act like twats and mess their own lives up then so be it.
Sometimes people need to learn the hard way.

You sound very kind and empathetic but for your own MH you need to take a step back.

Boododedoop · 09/01/2026 16:34

aerisgainsborough · 09/01/2026 13:56

She tries to make it my problem when she’s telling me the whole sordid story, crying because she’s left her husband for a much younger lad. Then asking for advice on how to ensnare him and should she send an anonymous message to the lad’s partner exposing their affair. Then she’s swearing me to secrecy and then fucks off down the other end of the country to play happy families with her in-laws. I can’t cope with things like this, my brain short-circuits. Maybe because I’m autistic, I don’t know. I’m normally resilient but this was too much. I feel how I feel.

You’re in an awful situation probably made worse for you by being autistic. I’ve no advice to give but I did want to offer you some support from afar.

Uhghg · 09/01/2026 16:41

InLoveWithAI · 09/01/2026 16:11

So you're autistic, but you think your sister has BPD? Why do you think it's BPD (an awful and quite rightly, now contested diagnosis) and not autism?

Your post is really judgy.

There’s a difference between BPD and autism.

Some things may overlap but to be diagnosed with autism you need to display certain behaviours such as communication difficulties, stimming, sensory issues, repetitive behaviours, hyperfixations, need for routines etc - most of which don’t form part of BPD.

I would assume OP would pick up on these traits if she’s ND herself.

It may be that she is ADHD hence the risky behaviour and changing jobs but that could also be part of BPD.

Or she could just be a bit of a drama queen.

toiletpaperthief · 09/01/2026 16:42

You need to learn boundaries OP, you seem to have a problem asserting them?. Just tell her in a polite way that you love her but she's stressing you out and no longer want to be her "confidant". You two have opposite personalities: she's the happy-go-lucky type and you're Mrs Stresses-out-very-easily.

You also sound quite judgemental and your sister sounds more fun.

JudgeJ · 09/01/2026 16:44

AnnieLummox · 09/01/2026 14:58

And then your parents went straight into “How could you put all this on your poor sister?” Did they even ask if B was alright, given her marriage has broken down? Or was it all about your stress?

I think that the OP's getting a really hard time here! B's marriage broke down because B fancied a bit of younger flesh and when it didn't work out her dopey husband let her back. The parents seem to be encouraging B to be a pain, to foist her self-inflicted problems on others then are blaming the OP. I wonder how many of those saying 'Stop her talking about herself' have ever encountered someone who really won't do that? Best bet is to walk away into another room, preferably one with a lock to stop B following with her trail of misery!

MissSnoop · 09/01/2026 16:46

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).

I'm audhd and the eldest of 3 sisters. I agree with the advice given here OP. I understand where you are coming from.

Working on being consistent with boundaries will help. I found the (audio) book Let them by Mel Robbins a good listen.

santasbaubles · 09/01/2026 16:46

The “grab a brew and a biscuit” makes me feel like you are enjoying all this drama to be honest.

StrippeyFrog · 09/01/2026 16:50

aerisgainsborough · 09/01/2026 14:03

Everything I have learned about my sister’s marriage this past few weeks has been against my will. She told me all of this and even when I told her it made me uncomfortable, she insisted on “getting it off her chest” because “it was killing her”. I work in mental health and it means I get taken advantage of sometimes because I’m kind and want to help.

I’m not really keen on her lifestyle because they’ve never grown up past about 20 and I don’t want to hear about her being tired from staying up gaming online when I spent half the night on the floor next to my disabled son’s bed because his melatonin hasn’t kicked in.

You need to be firmer with her. If she says she needs to get it off her chest then tell her to go find a therapist as she does not have the right to dump everything on you.

Same for the rest of the family. If they try to drag you into it just say why don’t you speak to B directly.

aerisgainsborough · 09/01/2026 16:55

TFImBackIn · 09/01/2026 16:28

I would be absolutely terrified if my sister was planning to meet a man who said something like that. I'd do anything to stop her from going there.

I think in future you need to say that no, she can't speak to you in confidence. She can't ask you to keep a secret. It's not fair on you. If she tells you anything it should be in the full realisation that you will tell at the very least your husband.

It’s terror that I was feeling. It’s very much outside of my frame of reference, the whole world of dating, kink and apps etc

OP posts:
justasking111 · 09/01/2026 16:57

Evaka · 09/01/2026 13:49

Agree :). Very good advice.

Excellent advice.

We have a family member like this. Younger generation, husband is a drip. She's always been a drama llama. It's worn thin now and we've all distanced ourselves.

Why women like this don't get divorced baffles me

ReadingTime · 09/01/2026 16:59

It’s not up to her who else you talk to about things, that’s up to you. You don’t need to keep anything secret from your husband.

If these conversations with B that you don’t want are happening on the phone, you can say I don’t want to hear about your relationship dramas, and if you carry on trying to tell me about this I’m going to hang up. If they are happening in person in your house, say the same thing, but say if you keep trying to tell me these things you will have to leave. The boundary you set isn’t what she does, it’s being clear about what you will do if she continues to do something that isn’t ok with you.

When she says “you have to promise not to tell anyone what I’m about to tell you” you can say no, I’m not making any such promise, just don’t tell me anything that you don’t want others to know.

You don’t have to always agree to do what she wants.

aerisgainsborough · 09/01/2026 17:00

santasbaubles · 09/01/2026 16:46

The “grab a brew and a biscuit” makes me feel like you are enjoying all this drama to be honest.

You’d think wouldn’t you? I really enjoy being stressed about and worrying about my sister when we’re both in our thirties and I have children of my own.

In reality, I myself was having a biscuit with my brew as I was typing. I added that line to the top at the end because I felt the length of the post required the disclaimer. Perhaps even adding levity to a situation that has been on my mind a lot.

OP posts:
Wateron · 09/01/2026 17:01

This reply has been deleted

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

Boododedoop · 09/01/2026 17:01

santasbaubles · 09/01/2026 16:46

The “grab a brew and a biscuit” makes me feel like you are enjoying all this drama to be honest.

I think it shows the Op was struggling when starting the thread so added the bit about the brew the biscuit because it’s something she’s picked up from others and decided to use it herself. The op is autistic and more than likely struggles with social norms.

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