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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:
zerored · 03/01/2026 03:42

You'll permanently damage your relationship with your son if you were to tell his girlfriend. He'll never trust you again.

Carla786 · 03/01/2026 03:43

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.

I disagree. Cheating is much more serious than that.

crumpet · 03/01/2026 03:44

I ageee with you in that I could not condone what he has done. I would probably have to say that I don’t want to see them together as a couple while the situation is as it is. This would mean that he has to sort his own airport transport and that I would not permit him to bring her to my house - I couldn’t sit there and pretend there is nothing wrong.

its up to him whether he tells her or not, but I couldn’t participate in his lies.

Carla786 · 03/01/2026 03:44

Jenpen31 · 03/01/2026 03:05

Oh dear. I get you are shocked and disappointed that it's happened under your roof.....but he is a grown man. Its not for you to get involved in his personal relationships. He has to make his own choices and mistakes at this age. Leave him to it. You have shown you disapproved. Leave it at that!
Maybe this is a sign that his girlfriend isnt actually the one for him and he may actually not be that happy with her if he has gone else where for affection so to speak.

Are you implying his gf isn't giving him enough affection? I hope you're not implying it's the gf's fault he's cheating.

ActiveTiger · 03/01/2026 03:45

Wow wow wow the amount of people saying not to say anything yet what if the one he cheated with has some sexual disease and he spreads it to gf wow can't believe the amount of people condoning it's ok for a long term gf to not know he is a cheat and actually hats off to mum for not sticking up for her son... different if you didn't know but you do and I would be very grateful if I was told tho hurt for health reasons

ErsBears · 03/01/2026 03:45

TheIrritatingGentleman · 03/01/2026 03:38

I didn't even think of that. So I've changed my mind, he really does need to tell her before because it could put her at risk.

Yes this is my issue, while I understand the view of people here and would take no pleasure in saying anything myself (and I likely won’t as the last thing I want to do is ostracise my son). I do find it extremely morally unsettling to sit back whilst he effectively takes away her ability to consent properly (by this I mean fully informed and aware of any risks). I adore my son, his choices have no bearing on my love for him, or the pride I feel for every other aspect of his life. But I struggle to sit back and watch him make a choice which is in my view anyway morally wrong.

OP posts:
Carla786 · 03/01/2026 03:46

Jenpen31 · 03/01/2026 03:13

I'd have a chat with him and ask him why he has done it.....you may find he isnt happy with this girlfriend or having doubts. Their relationship may not be all it seems. He is your son at the end of the day....he should be your priority. There must be a good reason as to why he has done it. There could be more to it.....

A good reason? There's never a good reason for cheating. Just because he's OP's son doesn't mean she had to downplay cheating.

Imagine if you were the gf..

Carla786 · 03/01/2026 03:47

Jenpen31 · 03/01/2026 03:20

Maybe he is building up to telling her....but hasnt had the opportunity to do so yet.....what with Christmas and then a holiday booked.....not really the right time.
I get where you are coming from....
But other then have a chat with him....I'd stay out of it.....and just remain polite with everyone. It's his life at the end of the day. He isnt married and there is no children involved.....Id stand back now.

It's the gf's life too. Pp have pointed out the STD risk..

moondip · 03/01/2026 03:51

I agree with how you feel and also that either he tells her or you do. He’s an adult, but he’s still your son, and you can still impact what he deems right and wrong and model to
him that actions have consequences. What will he take from it if his mother knew he cheated, in her home, and kept up his lie and acted as though nothing had happened in front of his girlfriend? I never get the people on here who say “they’re an adult” - so? I’m 33 and still take lessons from my parents. I would hardly expect my parents to act normal in front of my husband if I’d done something like that in their house.

Carla786 · 03/01/2026 03:52

ErsBears · 03/01/2026 03:23

If he has been waiting to break up with her then he could have waited to sleep with someone else?

I can’t believe people are actually making excuses for a grown man cheating on his girlfriend of two years! What happened to raising our sons to be men? Why are women so keen to give grown men ways out of their terrible choices.

Op, kudos to you for standing by your moral principles. I'm not saying you should tell her (I think ideally you should but I get worry re son's relationship with you) but you should strongly press son to do so if possible.

So many people on here seem to think general principles should fly out of the window when it's a family member. Your son is a grown man and needs to face up to his responsibilities. As you say, if we don't hold the men in our lives to account, how can we hope for change?

Don't make a decision now. Take some time to think it over, hopefully your son will come clean soon..

Sending a 🫂

FairyMaclary · 03/01/2026 04:00

I wouldn’t take him to the airport either. I wouldn’t put myself in a position where I become a liar.

As for those who say maybe he’s not happy! Well her son could retain some dignity and split up if he’s not happy, not become a lying cheat. A quick phone call to his girlfriend would do the job as they don’t live together. But instead he’s going on holiday with her! That’s having your cake and eating it. He’s clearly not bothered about the new woman if he’s going on holiday with his girlfriend. So I am guessing she was an opportunity he thought he could get away with.

There’s a notion that people can’t help but cheat. It’s romantic etc. stars aligning and colliding Soul mates.But in reality it’s all a bit grubby. And the cheater isn’t playing by the rules. They think they deserve more. And now he’s been caught he has excuses as to why he can’t tell her. The holiday. It will upset her etc.

This young woman may have passed on an STD. The girlfriend may get HPV or an STD which affects her future fertility. Cheaty McCheat may have been doing this for months. The girlfriend should the agency.

I wouldn’t be dragged into his lies. I wouldn’t be driving them anywhere. I’d say I love you and you brought your girlfriend into my life and I like her. I can’t lie to her (by omission) and she needs to be told so she can protect her future fertility. Sorry but I won’t drive around with her pretending I’m excited about your holiday. I can’t lie and I’m not playing happy families.

Yes he’s an adult but he has to face consequences of his choices and I would not be part of his lies. And if he doesn’t know this woman I’d be pissed he brought a stranger round my house for sex while I was away. My house is my home not a place for adult kids to have one night stands.

Mummyoflittledragon · 03/01/2026 04:03

I originally thought YABU to say something to her. However, thinking about the STD risk, I agree with you. Idk if you can actually say something to her. However, I would be reading the riot act with your ds and explaining if he has sex with his gf, he is knowingly spreading all kinds of bacteria to her. That internal / external micro abrasions during sex are common. These allow any harmful infections and diseases to go directly into the blood stream. That without knowing these risks, she isn’t giving her informed consent. Hopefully he will start to care about what he has done.

Is your ds contrite for inviting a random stranger into your home?

TheIrritatingGentleman · 03/01/2026 04:05

ErsBears · 03/01/2026 03:45

Yes this is my issue, while I understand the view of people here and would take no pleasure in saying anything myself (and I likely won’t as the last thing I want to do is ostracise my son). I do find it extremely morally unsettling to sit back whilst he effectively takes away her ability to consent properly (by this I mean fully informed and aware of any risks). I adore my son, his choices have no bearing on my love for him, or the pride I feel for every other aspect of his life. But I struggle to sit back and watch him make a choice which is in my view anyway morally wrong.

What you are saying is exactly how I would feel. I read this initially thinking of how to protect my relationship with my son, but also thinking of the girlfriends feelings. Now having been reminded about the implications, it's about health and consent.

He needs to understand that this isn't just a bit of harmless fun (not that anything is harmless about being cheated on), but could have further reaching implications.

Would he think it was okay if it happened to his daughter/sister/mother? What if he did have a daughter, you knew her partner of 2 years was sleeping with someone else and you said nothing - would his opinion be the same?

WarmGreyHare · 03/01/2026 04:05

I can't believe the amount of people saying don't get involved.
Lying, cheating and stealing are all things I feel very strongly about.
I would absolutely 'tell' on my child if they were doing any of those things. He has the opportunity to do it himself, but to expect you to not say anything while he is lying to her face in front of you? Absolutely not.

And by his reaction, I doubt this is the first time.
Doesn't sound like it was exactly a spur if the moment oops on a night out does it?

FrodoBiggins · 03/01/2026 04:06

YANBU
What does your DH think, out of interest?

ErsBears · 03/01/2026 04:06

Mummyoflittledragon · 03/01/2026 04:03

I originally thought YABU to say something to her. However, thinking about the STD risk, I agree with you. Idk if you can actually say something to her. However, I would be reading the riot act with your ds and explaining if he has sex with his gf, he is knowingly spreading all kinds of bacteria to her. That internal / external micro abrasions during sex are common. These allow any harmful infections and diseases to go directly into the blood stream. That without knowing these risks, she isn’t giving her informed consent. Hopefully he will start to care about what he has done.

Is your ds contrite for inviting a random stranger into your home?

He seemed rather more frustrated that we didn’t warn him we were coming back than actually remorseful!

He currently lives with some of his girlfriend’s close friends (that is how he met her) so I imagine he saw the opportunity to have someone over without anyone his girlfriend knows potentially catching him! I did ask if he knew the girl, he said sort of and I asked what sort of meant and he admitted they met on a dating app!

OP posts:
Makemeanonymous · 03/01/2026 04:07

I don't understand why pp think OP should refuse to be in the gf's company in the future. How on earth is the gf going to feel about that if she believes she has a good relationship with OP? She is going to wonder what has happened/ what she has done to annoy OP. And in effect OP woukd be punishing the gf for her son's appalling behaviour.

Personally I think.she should be having a heart to heart with her son and encouraging him to tell his poor gf . But if he refuses then I think OP should be telling the gf exactly what she discovered when she came home unexpectedly.

BlackCoffeeAndSugar · 03/01/2026 04:08

Dating app ffs gets wors4.

You are right op. Don't know why so many are keen to excuse cheating

Nicewoman · 03/01/2026 04:08

This reply has been deleted

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

FrodoBiggins · 03/01/2026 04:08

On a dating app makes me think he's probably done it before I'm afraid. So calculated - otherwise he's extremely unlucky to have got caught the first time ever

ErsBears · 03/01/2026 04:08

FrodoBiggins · 03/01/2026 04:06

YANBU
What does your DH think, out of interest?

He is very angry with DS, but doesn’t think we should tell his girlfriend as it’s not our business. I feel divided on that front as on one hand it’s not really our business, on the other hand sod who’s business it is if he is going to put his girlfriends health at risk, lie to her and take away any opportunity of informed consent.

OP posts:
99bottlesofkombucha · 03/01/2026 04:09

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.

She isn’t driving his employer to the airport for a holiday on Monday and welcoming them into the family so it’s not remotely comparable.

FrodoBiggins · 03/01/2026 04:09

@nicewoman are you sure you have the right username?? You think OP should be grateful he dog sat!?

TheIrritatingGentleman · 03/01/2026 04:11

he admitted they met on a dating app!

So it gets worse. This is one you've caught him out with, likely there have been others. Or he would like there to be others at the very least. I admire you for sticking to your morals on this. I hope if my daughter ever ends up in this situation she has someone like you advocating for her.

99bottlesofkombucha · 03/01/2026 04:12

Jenpen31 · 03/01/2026 03:20

Maybe he is building up to telling her....but hasnt had the opportunity to do so yet.....what with Christmas and then a holiday booked.....not really the right time.
I get where you are coming from....
But other then have a chat with him....I'd stay out of it.....and just remain polite with everyone. It's his life at the end of the day. He isnt married and there is no children involved.....Id stand back now.

Honestly you sound like even if there were children involved you’d defend him never seeing her or the children again and hiding money to not pay child support.

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