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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

My DS cheated on his girlfriend in my home

1000 replies

ErsBears · 03/01/2026 02:44

Hi, so DH and I were away staying with friends over new year, DS’s girlfriend had gone back to her home country to see her family and DS couldn’t as he had to work so I asked if he would be okay staying at ours to watch the dog, he said sure.
DH and I came home early as one of our friends has fallen ill and wanted some space, we went for dinner first then got a train and cab home at about 11:30pm. I didn’t pre warn DS as I didn’t really see the need to. When we got home he was in his room so I didn’t bother him but then DH realised we had no milk, nothing for breakfast and DH had a headache so needed some paracetamol. We have a 24 hour shop within driving distance and both DH and I had been drinking so I went to ask DS if he would mind popping out. I could see his light was on and hear the tv so knew he was awake. When I knocked on the door the first thing I heard was a girls voice saying “is that your mum”. He came the door in his boxers and asked why we were back early, I explained he told me he’d been drinking so couldn’t. Fine. I asked if his girlfriend was back early (I knew it wasn’t her as his girlfriend has a very identifying accent and it was clearly an English accent I heard).

Anyway he admitted he had someone else over, I told him that she had to leave, he booked her a cab and she left. I made it clear to him that either he tells his girlfriend tomorrow or as soon as she is back or I will tell her, I do not condone cheating. He tried to tell me he didn’t sleep with her but when I pointed out he was only in boxers he admitted he was lying. He said he would tell her but they have a holiday booked for next week (she gets back on Sunday, they fly out on Monday).

For context he’s 28, his girlfriend is 25 and they’ve been together for 2 years, they don’t live together but she owns a flat and he was meant to be moving in this year.

AIBU to be bloody raging and so disappointed that this is the man I raised? I am disgusted that he cheated and I think he needs to tell her before the holiday. We are meant to be picking them up on Monday morning to take them to the airport as it’s an early flight. I don’t think I can sit with her in the car and send her off on holiday with him knowing what he has done!

OP posts:
ErsBears · 03/01/2026 14:33

lessglittermoremud · 03/01/2026 14:30

Unless you’ve seen the engagement ring I’m guessing it doesn’t exist and he’s saying he brought it in an effort to get you to back off telling her.

Yes a good point really, I do find it hard to trust anything he says right now.

OP posts:
Nigglenaggle · 03/01/2026 14:36

Stand your ground OP I would be just the same. I would be disgusted with him and make my views absolutely clear and I wouldn't be able to lie by omission either. Good for you.

In addition to the disgustingness of cheating, he brought this relative stranger into your house behind your back. That would make me cross even if he was single.

HelloDenise · 03/01/2026 14:36

Venicelagoon · 03/01/2026 14:20

You need to talk to your son and explain your total disappointment in him seemingly stringing his girlfriend along. Sexual urges occur though. He lies to you and lies to his girlfriend too. But he should not expect you to play along with this too. Maybe money will be lost if he doesn't go on holiday as arranged with his girlfriend so hes going on the holiday anyway.

Oh right. Sexual urges occur. Fine. So anyone in a committed relationship is fine to scratch that itch with impunity? Jog on.

ScarletJune · 03/01/2026 14:37

My son did this admittedly he was 17/18. I understood his reasoning and felt empathy for him but was also furious. His gf was suspicious and asked me outright. I told her the truth, I refused to lie for him. In your situation, he knows exactly how you feel. Let them get a taxi to the airport and be there for support for them both when they get home. I hope he tells her the truth and maybe a week on holiday will give them time to discuss what happens when they get back. Good luck.

TwinklySquid · 03/01/2026 14:37

sourglitterfrog · 03/01/2026 02:57

I get that you are mad, and it is your business in so far that he had a guest over doing something immoral in your house.
I think it's a bit outrageous, however,that you would go against your son. You need to keep your oar out and not meddle in your 28 year old son's business. Would you call his employer if he was pulling sickies because you disagreed with his behaviour?
By all means, advise him but don't put yourself in the middle of this.

What happened to teaching our kids morals?

If I found out a child of mine had cheated, I’d say the same as OP. It is not fair to let the GF make a life based on lies. This is someone else’s life .

Staringintothevoid616 · 03/01/2026 14:42

ErsBears · 03/01/2026 03:08

For those saying I shouldn’t tell her if he doesn’t, what am I supposed to do if he simply never tells her? Just keep acting as though I don’t know something that could devastate her? Lie by omission every time I see her?
I don’t even know if I am capable of that. If he was so worried about her finding out that he didn’t want to tell her then he probably shouldn’t have cheated in the first place and certainly not in his parents home!

Yes. If you tell her it will destroy your relationship with your son forever. Something like 75% of men have cheated. Keep out of your grown son’s business. You can tell him you’re disappointed, but don’t go against his wishes. As a rule of thumb never get involved in someone else’s relationship

lessglittermoremud · 03/01/2026 14:43

ErsBears · 03/01/2026 14:33

Yes a good point really, I do find it hard to trust anything he says right now.

I think it’s all part of the manipulation I’m afraid, he’s not sorry, he’s sorry he’s been caught. He knows he is probably about to lose moving into her house, his easy life sharing a house with her best mates, a lovey holiday and everything else that went with their relationship.
You don’t accidentally download a dating app, meet a random, take them somewhere you’re not expecting anyone else to be just out of nowhere…
I say to my boys (thankfully younger and not quite independent) that there is no point in treating me as though i’m stupid when they think they can try and get something past me, I’m older, wiser and smarter.
Your Son is trying to say anything to get you to not say anything and pretend it was all a stupid mistake.

Jellycatspyjamas · 03/01/2026 14:44

CutePixieGirl · 03/01/2026 14:24

You should have informed him that you were returning early. That’s basic good manners.

Invading his privacy because you were too drunk to remember to get your own milk is just pathetic and rude.

You and your husband sound embarrassing and childish.

‘Raging’ at him is not going to make any difference to how he feels about what’s he’s done. If you have raised a decent person, he will already be feeling very bad, anxious and conflicted and as a parent, you should know this.

This should have been a quick, calm and quiet conversation between you and your son.

It’s her home, she’s not invading his privacy to return home early. If anything he’s disrespected her privacy by inviting some random person back to her house without her consent. You might be happy to have all and sundry invited into your home overnight by someone who no longer lives there, but I don’t think the OP is unreasonable to return to her own home unannounced.

TheFairyCaravan · 03/01/2026 14:45

Staringintothevoid616 · 03/01/2026 14:42

Yes. If you tell her it will destroy your relationship with your son forever. Something like 75% of men have cheated. Keep out of your grown son’s business. You can tell him you’re disappointed, but don’t go against his wishes. As a rule of thumb never get involved in someone else’s relationship

The grown son made it his mother’s business when he used her home for his one night stand.

Jellycatspyjamas · 03/01/2026 14:46

Staringintothevoid616 · 03/01/2026 14:42

Yes. If you tell her it will destroy your relationship with your son forever. Something like 75% of men have cheated. Keep out of your grown son’s business. You can tell him you’re disappointed, but don’t go against his wishes. As a rule of thumb never get involved in someone else’s relationship

And what about her wishes and morals. You’re expecting her to lie by omission to someone she has a relationship to spare her son’s feelings?

HelloDenise · 03/01/2026 14:47

CutePixieGirl · 03/01/2026 14:24

You should have informed him that you were returning early. That’s basic good manners.

Invading his privacy because you were too drunk to remember to get your own milk is just pathetic and rude.

You and your husband sound embarrassing and childish.

‘Raging’ at him is not going to make any difference to how he feels about what’s he’s done. If you have raised a decent person, he will already be feeling very bad, anxious and conflicted and as a parent, you should know this.

This should have been a quick, calm and quiet conversation between you and your son.

There is nothing cute about you. It's the OP's house. How in hell is going into your own house invading the dog sitter's privacy?

Factsoverfiction · 03/01/2026 14:48

If more parents behaved the way the op is instead of burying their heads and protecting their little soldiers, I wonder if that 75% figure would go down.

Nicewoman · 03/01/2026 14:49

ErsBears · 03/01/2026 14:28

He has spoke to me this afternoon and says he will tell her tomorrow as soon as she is back. He explained he doesn’t want to tell her today as she is having a big family get together with cousins she rarely sees and he doesn’t want to ruin that for her.

I asked why he downloaded the dating up in the first place and he said he didn’t know, I told him he needs to figure out why as she is inevitably going to ask.

He also confidentially told me that he has bought an engagement ring and really was planning to make a life with her so he doesn’t know what came over him. I again said that the why matters but not as much as what he’s done, no matter why he has done it, it’s wrong and he should think about if that’s the type of man he wants to be.

Well, that’s a much more serious dilemma if he was buying an engagement ring.

you need to ascertain if that is true or not, or if other posters have suggested, he’s saying that to get you off his back.

you need to softly encourage him that he needs to be truthful with you at all time and also truthful in how he interacts with girlfriends.

it’s right that he’s waiting for after the party, that’s basic consideration.

It would be helpful if both you and your DP sat him down to say cheating is absolutely unacceptable, that if he continues down this route, he will end up bitter and alone and never seeing his kids and end up with low calibre partners who also cheat on him.

I would try and get it out of him why he thought it was ok to cheat on someone he says he loves. Was he encouraged by friends? Work colleagues? Some online websites? Etc.

he also needs to hold off buying an engagement ring as he could well find that once he tells his gf that she instantly dumps him, gets her friends to throw all his belongings on the road, taken to the tip, sold online, and he never hears from her again.

if he thinks his gf will have a cry, be angry for a few days, then carry on as normal, he’s in for a rude awakening. He needs to brace himself for an onslaught of rage and being dumped.

Essentially, he needs to understand the causal connection between cheating & relationships terminating. And realise thank God he came to his senses now and not be continuing with this hedonistic cheating lark into his 30s/40s/50s etc.

best of luck!

ChocolateBiscuitsandaCuppa · 03/01/2026 14:49

Am a bit late to this but am blown away by the people saying you should, 'mind your own business' etc. Who are these people? Would they not be horrified and heartbroken if someone they were planning on building a life with cheated on them at the first easy opportunity for casual sex, and didn't give an ounce of consideration for their health?

Good on you for calling out someone in your life you care about, and good on you for having standards. It's no different to calling out a friend for having unacceptable values.

Catza · 03/01/2026 14:50

For those people who keep saying the OP will lose her son's trust, I'd just like to draw your attention to the fact that it wasn't a situation where the son came to her to admit he's been cheating and also for her motherly advice or reassurance, repented for his mistakes and begged her not to give him away. He was caught. Accidentally. Had it not been the case, the OP would never have known. It's not the situation where trust is in question.. It's a situation where a grown man tries to deceive everyone for his own benefit.

JayJayj · 03/01/2026 14:52

With what you’ve said about wages etc. I’m wondering if the reason he doesn’t want to break up is because of the living situation. He’s probably fed up of house sharing and moving into her flat, owned out right, he will be saving money.
As you said, she needs to be able to make an informed decision. If she decides to stay with him then at least she knows.

Carla786 · 03/01/2026 14:54

Tartanboots · 03/01/2026 11:37

It's none of your business, he's a grown up. I can see why you don't like it though.
He's not cohabiting or married and there are no kids involved, he doesn't live with you, he won't appreciate his mum interfering.

He's about to move in.

So you think cheating isn't that serious if you're not yet cohabiting?

KitWyn · 03/01/2026 14:54

CutePixieGirl · 03/01/2026 14:24

You should have informed him that you were returning early. That’s basic good manners.

Invading his privacy because you were too drunk to remember to get your own milk is just pathetic and rude.

You and your husband sound embarrassing and childish.

‘Raging’ at him is not going to make any difference to how he feels about what’s he’s done. If you have raised a decent person, he will already be feeling very bad, anxious and conflicted and as a parent, you should know this.

This should have been a quick, calm and quiet conversation between you and your son.

It's their house, and he's their son. I'd expect a loud "Hello, we're back early" holler when they get through the door. And also (always!) a knock on the bedroom door. But that's it.

Their 28-year old son used the opportunity provided by dog-sitting, to bring a strange woman he found on an app, to have sex in his parents' home. So, he was hiding his shagging and cheating, somewhere he no long lives.

It's scummy behaviour, and he's the one who is embarrassing and childish.

It was probably the son who used up the last of the milk without replacing it. Though that's the least of his many failings.

bringbacksideburns · 03/01/2026 14:55

I’m with you OP - but I’m not surprised so many people are saying keep out of it.

We have a duty as parents to guide our kids and when they have behaved badly even as adults we should never stay silent and condone actions like this. Ironically some of these posters will have suffered at the hands of cheaters
.
I would feel just like you. You build up a relationship with your child’s partner when you are talking years. I am far too open and hate secrets. I would never tell the girl myself but I’d make damn sure he thought I would. She deserves better. He knew exactly what he was doing when he downloaded that app. He may probably have done it before.

If they work it out that’s down to them but she needs to know.

PrettyPickle · 03/01/2026 14:55

Further to my last post, I have just seen that he picked his bit on the side up from a dating app and that he reckons he wants to marry his girlfriend. Sorry this sounds like he is trying to coerce you here inn to keeping quiet.

Lets get this right, when the opportunity presented itself to have a fling, he got on a dating app and shagged someone else because he thought no-one would know? He has betrayed her, you and his housemates but mainly himself. He is not sounding like a decent or trustworthy person despite the great moral guidance he has had from his parents..

This was pre-meditated, because its just way too convenient that he only registered on the dating app that day (I don't believe this) when he had your home to use and he pulled straight away and that being the case, its hardly the actions of a man in love, so I doubt its the first time.

I would truly read him the riot act and make your feelings clear but I still don't think you should tell the girlfriend as I believe you have already decided. He needs to face the music.

And then to try coerce you into staying quiet he says he wants to get engaged to his girlfriend - the poor cow!

BestZebbie · 03/01/2026 14:55

Nicewoman · 03/01/2026 14:49

Well, that’s a much more serious dilemma if he was buying an engagement ring.

you need to ascertain if that is true or not, or if other posters have suggested, he’s saying that to get you off his back.

you need to softly encourage him that he needs to be truthful with you at all time and also truthful in how he interacts with girlfriends.

it’s right that he’s waiting for after the party, that’s basic consideration.

It would be helpful if both you and your DP sat him down to say cheating is absolutely unacceptable, that if he continues down this route, he will end up bitter and alone and never seeing his kids and end up with low calibre partners who also cheat on him.

I would try and get it out of him why he thought it was ok to cheat on someone he says he loves. Was he encouraged by friends? Work colleagues? Some online websites? Etc.

he also needs to hold off buying an engagement ring as he could well find that once he tells his gf that she instantly dumps him, gets her friends to throw all his belongings on the road, taken to the tip, sold online, and he never hears from her again.

if he thinks his gf will have a cry, be angry for a few days, then carry on as normal, he’s in for a rude awakening. He needs to brace himself for an onslaught of rage and being dumped.

Essentially, he needs to understand the causal connection between cheating & relationships terminating. And realise thank God he came to his senses now and not be continuing with this hedonistic cheating lark into his 30s/40s/50s etc.

best of luck!

If he was hoping to get engaged then it is absolutely vital that his GF finds out how he behaved in full asap - at present the risk to her is a potential STD, lack of informed consent to ongoing sex, having a boyfriend who doesn't actually respect her as much as she believes he does..........but once he moves in with her or they get engaged then she has even more to lose from finding out and then dumping him, and if he manages to marry her without her finding out what he is like, he could steal half her flat! (and it would be stealing as she is likely not to consent to marrying if she knows what he did, so the union would be entered into under false pretences).

TheFairyCaravan · 03/01/2026 14:55

CutePixieGirl · 03/01/2026 14:24

You should have informed him that you were returning early. That’s basic good manners.

Invading his privacy because you were too drunk to remember to get your own milk is just pathetic and rude.

You and your husband sound embarrassing and childish.

‘Raging’ at him is not going to make any difference to how he feels about what’s he’s done. If you have raised a decent person, he will already be feeling very bad, anxious and conflicted and as a parent, you should know this.

This should have been a quick, calm and quiet conversation between you and your son.

Like fuck would I be notifying anyone that I was returning to my own home, the one I pay for, earlier than anticipated.

It’s basic manners, imo, not to use your parents’ house as somewhere to have casual sex especially when you’re supposed to be in a committed relationship.

Yorkshirelass04 · 03/01/2026 14:56

I bet this isn't the first time he's cheated. It's too bold a scenario for a first time cheater. He's just not been caught.

usedtobeaylis · 03/01/2026 14:56

The mention of an engagement ring, whether it actually exists or it, makes it all the more important for the girlfriend to have all the facts about the kind of person her boyfriend is and what he has done. Maybe she'll forgive him, maybe she won't, but her future should not be hinged on anyone covering up for her boyfriend.

Carla786 · 03/01/2026 14:59

peacefulpeach · 03/01/2026 12:15

😂😂🙈 contrary to your user name I expect you’re actually a horribleman..

Just my thought..

What kind of 'woman' writes ominously 'women are very Wiley' & similar as this person did in the deleted post?

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