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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Is this illegal?

373 replies

CarlStoleMyUnderpants · 04/03/2026 14:12

Discovered someone is cheating on his wife and have contacted two of his siblings to tell them so they can surreptitiously investigate and look out for the wife. I can't prove it as it would be hearsay, but I hoped they'd try and look at his devices or keep an ear out to gain evidence. Have I gone too far? I absolutely know this is happening.

OP posts:
LiviaDrusillaAugusta · 04/03/2026 19:02

Amandasummers · 04/03/2026 18:58

@CarlStoleMyUnderpants you’re not losing her over a snake of a man, you’re “losing” her because she has the morals of an alley cat. I wouldn’t want her as a friend!

I think you’ve made a wrong move going to his siblings. You should have gone to someone that the wife is associated with if you didn’t want to go to her directly but personally I’d have just gone to the wife, I’d sure as hell want someone to tell me if I was her. If the siblings are anything like the man in question then he simply has a heads up now and plenty of time to cover his tracks if he does get caught.

If she doesn’t know the wife enough or doesn’t have the guts to speak to her, then she should keep her nose out.

Lookskywalker · 04/03/2026 19:04

ticketwoes · 04/03/2026 18:18

God, some of these responses baffle me.

if anyone ever found out my partner was cheating on me and they told me I’d not think they were a busy body, I’d be bloody grateful that they decided to not let me carry on with my life looking like a fool.
I’d be furious with anyone who knew and didn’t see fit to tell me.

But they haven’t told the wife?

scottishgirl69 · 04/03/2026 19:05

BauhausOfEliott · 04/03/2026 15:43

Reading through all the OP's posts in this thread, I'm pretty sure that their concerns about illegality probably stem from the fact that there is a hell of a lot more to this story - specifically about her own behaviour - than she's letting on.

Put it this way, I wouldn't be surprised if another thread popped up at some point along the lines of 'A distant acquaintance of mine has become convinced that my husband is cheating on me and her behaviour towards him has now reached the point where it could be construed as stalking. She's devoted hours and hours of her life to trying to prove he's cheating, including contacting his siblings - she's never even met him, let alone them. AIBU to speak to the police now?'

I was stalked in 2018 for 18 months. Online - but it crossed over to my offline life. My name was handed over to these people. They found my address -(because I used to run my own business). They tweeted photos of my house. Several times with the words "tick tock" you're going down. There was an open threat to maim me tweeted. I lived in fear for a long time. Police did nothing. They sent a package to my house as a warning to me - we know where you are - that was before they tweeted photos of my house. (They've also done the same to more than other person that I know of, not always single women but mostly - several went to police and got nowhere). There are hate accounts dedicated to me on twitter - some of them are still up. They reported me for benefit fraud that I was not committing and I had to go through a compliance interview - but that's allowed obviously - people can make allegations of benefits fraud even if there's no substance to them.

My personal details were also posted on a doxxing Blog (hosted in China - because if it had been hosted in the UK I believe that the man who ran it would have been arrested due to the threats that were on it)

Contacting someone once - won't be construed as stalking - particularly if there's no threats been made. I had to contact police again in January of this year - because of a continuation of what was going on. The person concerned has doxxed me multiple times on twitter. They've outed my location multiple times too, that went on for over two years.

They've sent me communication that I would consider as extremely intimidating - to my phone - my number was handed over by a third party - there were no threats though - and if there aren't threats - there's often very little police can do

I personally think the OPs behaviour isn't section 39 but even if it were - it might surprise people how little (some) police do for people who are actually in fear

AmyWinemouse · 04/03/2026 19:05

IrrationallyAngry · 04/03/2026 17:35

@CarlStoleMyUnderpants I've read the whole thread but maybe I've missed something. You say you are friends with the affair partner but not the man cheating. How do you know his brother and sister's contact details? Especially since you didn't know the sister was NC with him so can't be friends with them?

Angry Shake GIF by angy frog

Maybe she met them at the Mexican disco

ticketwoes · 04/03/2026 19:07

Lookskywalker · 04/03/2026 19:04

But they haven’t told the wife?

No, I know. I said up thread that I don’t understand their thinking regarding telling his siblings.

I do think the OP is correct though and the sentiment would be the same from some if she had.

scottishgirl69 · 04/03/2026 19:14

CarlStoleMyUnderpants · 04/03/2026 14:17

Mumsnet doesn't like that. I'd be accused of blowing her life up, of interfering, told she probably knows anyway, they are swingers, that sort of thing. I thought this way someone could try and find some evidence and then confront him.

Her life is going to blow up anyway - irrespective of who tells her.

TheAverageJoanne · 04/03/2026 19:19

scottishgirl69 · 04/03/2026 19:14

Her life is going to blow up anyway - irrespective of who tells her.

Maybe nobody will tell her because they think the OP is crazy, interfering, lying or batshit and she's none the wiser and she'll carry on being at risk of STDs and her agency and consent being stolen.

Scarlettpixie · 04/03/2026 19:21

I don’t get why you feel the need to interfere. The only decision you should be making is if you want to stay friends with the affair partner who is your friend.

dadtoateen · 04/03/2026 19:31

TheAverageJoanne · 04/03/2026 19:19

Maybe nobody will tell her because they think the OP is crazy, interfering, lying or batshit and she's none the wiser and she'll carry on being at risk of STDs and her agency and consent being stolen.

I’m sorry I don’t understand?

agency and consent being stolen?

why at risk of std’s? You know people use condoms sometimes…

scottishgirl69 · 04/03/2026 19:57

dadtoateen · 04/03/2026 19:31

I’m sorry I don’t understand?

agency and consent being stolen?

why at risk of std’s? You know people use condoms sometimes…

She doesn't know her husband is having an affair and she's continuing to sleep with him without knowing this - and some people don't use condoms - if the woman is on the pill or other kinds of contraception

TheAverageJoanne · 04/03/2026 19:57

dadtoateen · 04/03/2026 19:31

I’m sorry I don’t understand?

agency and consent being stolen?

why at risk of std’s? You know people use condoms sometimes…

Are you being deliberately obtuse? Women who continue to think they're in a monogamous relationship when they're actually being deceived is having the ability to govern her own life undermined.

scottishgirl69 · 04/03/2026 20:02

dadtoateen · 04/03/2026 19:31

I’m sorry I don’t understand?

agency and consent being stolen?

why at risk of std’s? You know people use condoms sometimes…

You made a post on a thread the other week - that was very flippant and it ended up being removed by the mods as far as I'm aware. It was on a thread to do with sex and I remember thinking - I hope your teen isn't a girl. You really seem to have some strange ideas about women. It should not need to be pointed out to you that if someone is having an affair that they are potentially putting the person who doesn't know about said affair at risk sexually

Lookskywalker · 04/03/2026 20:03

scottishgirl69 · 04/03/2026 20:02

You made a post on a thread the other week - that was very flippant and it ended up being removed by the mods as far as I'm aware. It was on a thread to do with sex and I remember thinking - I hope your teen isn't a girl. You really seem to have some strange ideas about women. It should not need to be pointed out to you that if someone is having an affair that they are potentially putting the person who doesn't know about said affair at risk sexually

This.

Onlyhereforthebatshitneighbours · 04/03/2026 20:03

Fgs why have you turned this mess into some sort of Shakespearen play??

Just tell the poor woman what you know!

dadtoateen · 04/03/2026 20:03

TheAverageJoanne · 04/03/2026 19:57

Are you being deliberately obtuse? Women who continue to think they're in a monogamous relationship when they're actually being deceived is having the ability to govern her own life undermined.

No, why would I? No need to get nasty, was a genuine question.

plot twist….. she knows all about it! 😵🤣

scottishgirl69 · 04/03/2026 20:04

TheAverageJoanne · 04/03/2026 19:57

Are you being deliberately obtuse? Women who continue to think they're in a monogamous relationship when they're actually being deceived is having the ability to govern her own life undermined.

An ex of mine cheated on me around 20 years ago. It went on for three months. I didn't know about her and she obviously didn't know about me. My first comment was that he had potentially put my sexual health at risk-he just laughed and said he got off on the fact that he was sleeping with both of us at the same time.

Lookskywalker · 04/03/2026 20:05

dadtoateen · 04/03/2026 20:03

No, why would I? No need to get nasty, was a genuine question.

plot twist….. she knows all about it! 😵🤣

What’s funny?

dadtoateen · 04/03/2026 20:06

scottishgirl69 · 04/03/2026 20:02

You made a post on a thread the other week - that was very flippant and it ended up being removed by the mods as far as I'm aware. It was on a thread to do with sex and I remember thinking - I hope your teen isn't a girl. You really seem to have some strange ideas about women. It should not need to be pointed out to you that if someone is having an affair that they are potentially putting the person who doesn't know about said affair at risk sexually

Another personal
dig that is unnecessary. Yes I have a daughter, shock horror that had her shithouse of a mum abandon her, shocker, some women are total bellends.

anyway, I’m out of this one, it’s of course all the man’s fault on this one 👍

DotAndCarryOne2 · 04/03/2026 20:07

TheAverageJoanne · 04/03/2026 18:24

Well aren't you a treat?

Yep, and she’s right.

scottishgirl69 · 04/03/2026 20:07

dadtoateen · 04/03/2026 20:03

No, why would I? No need to get nasty, was a genuine question.

plot twist….. she knows all about it! 😵🤣

I don't know why you think any of this is funny - but I'm not surprised. At all. Plot twist she knows about it? And what if she doesn't know about it? What if she doesn't know her husband is having an affair and sleeping with someone behind her back?

Affairs cause damage - and it can be to all parties involved - not just the person who doesn't know

dadtoateen · 04/03/2026 20:07

This reply has been deleted

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

NoSoupForU · 04/03/2026 20:07

Fucking hell. If some stranger messaged me telling me that my brother or sister were having an affair I'd think they were mental. I hope you didn't start suggesting to them that they need to check his phone as whilst it isn't illegal for you to do it, it is way beyond the boundaries of normal behaviour.

dadtoateen · 04/03/2026 20:08

scottishgirl69 · 04/03/2026 20:07

I don't know why you think any of this is funny - but I'm not surprised. At all. Plot twist she knows about it? And what if she doesn't know about it? What if she doesn't know her husband is having an affair and sleeping with someone behind her back?

Affairs cause damage - and it can be to all parties involved - not just the person who doesn't know

Affairs absolutely do ruin lives, cheaters are horrible people, male or female.

scottishgirl69 · 04/03/2026 20:13

dadtoateen · 04/03/2026 20:06

Another personal
dig that is unnecessary. Yes I have a daughter, shock horror that had her shithouse of a mum abandon her, shocker, some women are total bellends.

anyway, I’m out of this one, it’s of course all the man’s fault on this one 👍

Stop press my dad walked out on me when I was three. Hasn't had any contact since and doesn't give a toss

Don't patronise me on this. I know fine well not all women are decent when it comes to men - but that isn't what we are talking about here

SouthernNights59 · 04/03/2026 20:16

CarlStoleMyUnderpants · 04/03/2026 16:22

There is nothing more to it that I am not letting on. A friend of mine is shagging a married man. I found out it's been going on for nearly 4 years and I know the wife in passing. Nothing more than that. What are you suggesting?

Given that neither the wife or husband are your friends, or even people you know well, you should be keeping your nose out of it. The only person you should be bothering about is your friend. I don't understand people like you who somehow think they have the "right" to interfere in other people's lives.

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