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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:
Sahara123 · 04/03/2026 16:21

Lookskywalker · 04/03/2026 15:09

Yeah I was thinking the same. I can’t imagine sibs beating up their brother because he’s having an affair.

And if someone came to me with this news about my sibling I’d be shrugging my shoulders and keeping out of it , realistically what could I do ?

CarlStoleMyUnderpants · 04/03/2026 16:22

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?'

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?

OP posts:
CarlStoleMyUnderpants · 04/03/2026 16:23

raspberets · 04/03/2026 15:44

I get the impression OP is a bloke,

I'm absolutely not a bloke.

OP posts:
Grizelina · 04/03/2026 16:25

By the sounds of it the affair person is a nanny who is sleeping with her employer's husband "brought up their children". How do you know that the wife doesn't know already - some women are quite happy to keep up outward appearances (anniversary posts on Facebook) and ignore their spouse's behaviour. Whilst not doing anything illegal it's highly possible that you will have thrown a bomb into their lives by telling siblings - you have no idea how they might share this news with others.

Rather than telling the siblings you should have told your "friend" that unless she broke things off with him you were going to tell his wife. However what's done is done now so you'll just have to wait and see what happens. Going forwards you shouldn't meddle with things that, however well intentioned, are really none of your business - not everybody has the same moral standards.

Thanksforyourlackofthought · 04/03/2026 16:26

Let’s say the siblings say something to the wife. And the wife confronts your friend. And then your friend asks you if you said anything because you were the only person who knew? What do you intend to tell your friend?

CarlStoleMyUnderpants · 04/03/2026 16:30

Grizelina · 04/03/2026 16:25

By the sounds of it the affair person is a nanny who is sleeping with her employer's husband "brought up their children". How do you know that the wife doesn't know already - some women are quite happy to keep up outward appearances (anniversary posts on Facebook) and ignore their spouse's behaviour. Whilst not doing anything illegal it's highly possible that you will have thrown a bomb into their lives by telling siblings - you have no idea how they might share this news with others.

Rather than telling the siblings you should have told your "friend" that unless she broke things off with him you were going to tell his wife. However what's done is done now so you'll just have to wait and see what happens. Going forwards you shouldn't meddle with things that, however well intentioned, are really none of your business - not everybody has the same moral standards.

I meant the wife had brought up the children, no she isn't a nanny.

OP posts:
Hoppinggreen · 04/03/2026 16:31

I am a Lawyer and this is most certainly illegal under section 2.47 of the Dontbeagrass legislation

JTRSOP · 04/03/2026 16:34

CarlStoleMyUnderpants · 04/03/2026 14:14

Getting in touch with his brother and sister

😂😂

JustAnotherWhinger · 04/03/2026 16:34

CarlStoleMyUnderpants · 04/03/2026 15:24

No. I was only concerned about the malicious communication aspect. I'm so pissed off with my friend for doing it I'm not bothered about that, though it's a shame to lose a 20+ year friendship over a snake of a man.

You wouldn’t be losing the friendshio over “a snake of a man” you’d be losing it over her crap behaviour.

She’s not an unwitting victim being conned by someone she thinks is single.

CarlStoleMyUnderpants · 04/03/2026 16:37

JustAnotherWhinger · 04/03/2026 16:34

You wouldn’t be losing the friendshio over “a snake of a man” you’d be losing it over her crap behaviour.

She’s not an unwitting victim being conned by someone she thinks is single.

True. When I asked her how she could do this and to think of the wife, who's having her agency removed, (she has been cheated on herself in the past) her reply was "I'm not bothered".

OP posts:
runningonberocca · 04/03/2026 16:38

I wouldn’t be impressed at being asked to spy on my sibling. If it’s that important to you tell him you know and that you are giving him a chance to tell his wife or else you will tell her. No need to drag the whole family in You sound like you’re loving the drama

CarlStoleMyUnderpants · 04/03/2026 16:41

runningonberocca · 04/03/2026 16:38

I wouldn’t be impressed at being asked to spy on my sibling. If it’s that important to you tell him you know and that you are giving him a chance to tell his wife or else you will tell her. No need to drag the whole family in You sound like you’re loving the drama

I really do not love or like drama of any kind. I hate what is happening and maybe I had a knee jerk reaction by contacting the people I did, but no I don't want any drama in my life at all.

OP posts:
Tooconfused12 · 04/03/2026 16:42

God I wish people would keep their fucking noses out of other people’s business.

You have potentially just thrown a hand grenade into multiple people’s lives because you decided it was the right thing to do. Based on what? Why?

Seriously - shame on you. You know nothing about what goes on behind closed doors so back off 😡 You will not be thanked for this - has it ever crossed your mind that some people don’t want to know or can’t deal with the fallout?

You should never have interfered

CakeMeHomeIveSeenEnough · 04/03/2026 16:43

If you were going to tell anyone, the wife is the one. Yes, some people on MN will say you could be blowing up her life or that she may be thrilled to the tips of her toes that her husband is sleeping with someone else (because that's so common). So what? If you feel strongly about it, you can still tell people what you know or suspect. It's not illegal.

Telling his family is unlikely to do much except possibly warn him that he needs to do more to hide his affair. Even if they tell him to stop and he listens, he's already cheated. He's tasted the forbidden fruit and will likely go back for more. If I were the wife, I think I'd want to know the truth and be given the chance to make up my own mind about what to do. The person telling the painful truth isn't the problem; the unfaithful husband is.

And yes, dump your disgusting loser of a friend.

Moonnstarz · 04/03/2026 16:43

Why are you getting involved? You say you don't like drama but are clearly happy to message siblings!

Laura95167 · 04/03/2026 16:44

Want a spoon for all that stirring youre doing?!?

Its defo not illegal to tell someone, someone else is cheating.

I do think its weird to do it "hoping" they'll hack his devices (which could be - depending on a variety of factors) or gather evidence to "look out" for their sister in law.

If you told me my brother was cheating. Id likely not believe you, but either way publicly tell you to mind your own business and leave my brother alone. Privately I might tell him what id learnt and ask him is there any truth to it and if so WTAF. But I absolutely, definitely wouldnt spy on him on the basis of some rumour, or even "evidence". When the "evidence" isnt enough for you to do anything but attempt to encourage me to look for more.

I think you should either mind your own business or depending on who you are in relation to these people confront the cheater or tell the wife. I dont think stirring it is ever reasonable, helpful or protective.

Shatteredallthetimelately · 04/03/2026 16:50

CarlStoleMyUnderpants · 04/03/2026 16:37

True. When I asked her how she could do this and to think of the wife, who's having her agency removed, (she has been cheated on herself in the past) her reply was "I'm not bothered".

They don't tend to be bothered...more into ruining other peoples lives than caring about how the wife would feel.

Dancingintherain09 · 04/03/2026 16:53

Personally, I would tell the wife. If my husband was doing something he shouldn't I'd want to know rather than living in delusion. Even an anonymous tip off would be better than nothing. You will probably find his siblings may already know and will cover for him give him a heads up to hide stuff.
If you imagine yourself in her position, would you want to know? And if you imagine this still going on in five years, how would you feel then?
Also consider the practical realities: Are you prepared for possible denial, backlash, or being pulled into conflict? Are you willing to be identified as the source? What boundaries would you need in place, anonymity?
There isn’t a clean or painless option, focus on choosing the path that aligns most with your integrity

dadtoateen · 04/03/2026 16:59

Hoppinggreen · 04/03/2026 16:31

I am a Lawyer and this is most certainly illegal under section 2.47 of the Dontbeagrass legislation

Love this reply :)

Beachtastic · 04/03/2026 16:59

I don't know why everyone is being horrible to OP!

CleanSkin · 04/03/2026 17:02

By contacting the siblings & asking them to investigate , do you think you’ve effectively handed all responsibility to them?
If so, just let it play out as it’s not your circus any more.

If you don’t think they now have control, please tell the wife asap.

BauhausOfEliott · 04/03/2026 17:03

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?

I'm suggesting that you are colossally over-involved and that contacting someone's siblings about their brother to try and gather material proof that he's cheating on his wife - a woman you barely know - is intensely intrusive and OTT in relation to someone else's marriage. It's not proportionate behaviour and you sound very obsessive and possibly a bit unwell.

Wingingit73 · 04/03/2026 17:05

Bit of a busy body. This could really backfire on you. Not illegal

butterpuffed · 04/03/2026 17:07

If the wife is only known to you 'in passing' , how do you know her sister-in-law and brother-in-law to be able to contact them about the affair ?

DotAndCarryOne2 · 04/03/2026 17:08

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?

I don’t understand why you think it’s any of your business to be honest. How did you ‘find out’? Because if it’s in any professional or confidential capacity, then yes, it could very well come back to bite you. You say you don’t like drama but I’ll wager there’s a truck load of it coming your way when the wife finds out and confronts everyone, and it dawns on your friend that the only person it could have come from is you.

If you know beyond doubt that these two are having an affair why are you asking the siblings to look for more proof ? Why don’t you just tell the wife yourself because it’s bloody obvious you can’t wait for the shit to hit the fan.

OP l think this is either rage bait, or you’re completely over invested, to the point of being unwell.