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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:
thepariscrimefiles · 03/01/2026 16:04

Jane143 · 03/01/2026 15:20

I’d stay out of it. Let him enjoy his imminent holiday and maybe if it goes well he will decide she’s the one. He’s young. Men don’t settle and marry so early nowadays. After the holiday is the time to talk. If you tell him today it will ruin a costly holiday for them both.

He shouldn't be able to enjoy his holiday if he hasn't told his girlfriend what he has done before they go. Otherwise, she is there under false pretences, thinking that she had a loving and faithful boyfriend when she absolutely has not. It could also put her sexual health at risk if they have sex without him using a condom.

The one person that nobody could argue has done something wrong is the girlfriend. She currently isn't in possession of important facts about her relationship and she needs to know before going on holiday.

Doone22 · 03/01/2026 16:04

I might feel bad for his girlfriend but would never in a million years start something with my son like that. It makes me feel like you have unresolved issues with cheating and are taking it out on him. He has to live his own life and learn for himself.
I might not like it but I would never force him to confess. He has to sort his own life out. I would only go so far as to say please respect your own property as you don't want strange there. Plus I wouldn't tell lies to his gf for him .

JHound · 03/01/2026 16:06

Thank you OP for being a decent person. You were right to throw her out and right to tell your son to tell his girlfriend. It’s theft of consent otherwise. I would not necessarily say it’s your place to tell but he needs to.

What a disgusting excuse of a man.

Uricon2 · 03/01/2026 16:07

Nicewoman · 03/01/2026 15:56

Yes, it’s important you and your DP are singing from the same hymn sheet.

I do think she should be told before the holiday, otherwise the whole holiday will be remembered for fakery. See if he can get money back on the holiday or sell on the holiday to others.

I think he’s just too immature for a serious relationship and needs to sow his wild oats until he himself understands sacrifice, loyalty and hard work that goes into a relationship. He must want to do it himself, not be reminded by others to toe the line. Otherwise he will forever think oops, gf gone to the shops, let’s text the latest love interest.

You've changed your tune a bit @Nicewoman

Your post on this thread at 4:41 this morning (one of many in a similar vein, some now deleted)

It’s not that, it’s why you think you can interfere & dictate who your adult almost 30-year old son can date? It’s like you’re stabbing him in the back & you will destroy all trust you have with him. Just so you can feel morally superior.
incidentally, the son’s gf probably doesn’t have a flattering opinion of you either before you start dreaming of buying wedding dresses & weddings in Tuscany. Foreign gf is wise to her flirty bf and has already planned her exit speech.

BestZebbie · 03/01/2026 16:07

Doone22 · 03/01/2026 16:04

I might feel bad for his girlfriend but would never in a million years start something with my son like that. It makes me feel like you have unresolved issues with cheating and are taking it out on him. He has to live his own life and learn for himself.
I might not like it but I would never force him to confess. He has to sort his own life out. I would only go so far as to say please respect your own property as you don't want strange there. Plus I wouldn't tell lies to his gf for him .

A major part of sorting his life out at his point is learning is that most people (currently around 70% on this thread) have issues with cheating, and that cheating is likely to have negative consequences for him eventually.

PatsyJane · 03/01/2026 16:07

I think it was unreasonable not to warn your son you were coming home early. In fact I’m not sure this an actual true post tbh. Who wouldn’t warn family they were arriving unexpectedly at 11.30pm and then starts drinking and then asks son i his bedroom to go and get paracetamol and milk?
If it is all true i’d have pretended not to notice the woman and wouldn’t have questioned my son. It’s between him snd his girlfriend but now you know you know so you’ve put yourself in a difficult position.

JHound · 03/01/2026 16:08

Justsoupsetrn · 03/01/2026 03:06

Other posters saying it's none of your business but there's so many threads where the exes mum knew he was cheating / cheated and everyone's said how horrible the MIL's are for not saying anything

This is AIBU OP, you'll have people saying your unreasonable for not saying and being saying your unreasonable for saying

If it was my DS I'd want to tell her if he didnt, but I'm not sure I'd actually be able to. But then again, I wouldn't feel comfortable spending time with her again with somthing so horrible hanging over me 😭

I assume the posters telling her to stay out of it are BoyMoms (TM).

As you point out they would not be so understanding if the GF were their daughter or if they learned their husband was cheating and the MIL knew

HelloDenise · 03/01/2026 16:09

Redpeach · 03/01/2026 15:30

The downloading the app just to get sex with a stranger makes it all the more seedy

I don't think he did that. I think that's an excuse.

JHound · 03/01/2026 16:09

PatsyJane · 03/01/2026 16:07

I think it was unreasonable not to warn your son you were coming home early. In fact I’m not sure this an actual true post tbh. Who wouldn’t warn family they were arriving unexpectedly at 11.30pm and then starts drinking and then asks son i his bedroom to go and get paracetamol and milk?
If it is all true i’d have pretended not to notice the woman and wouldn’t have questioned my son. It’s between him snd his girlfriend but now you know you know so you’ve put yourself in a difficult position.

Why would anybody “warn” somebody they were going back to their own home early?

Hicupping · 03/01/2026 16:09

All these excuses for his awful behaviour. Boys will be boys is still alive and kicking. Maybe it will do him some good to learn consequences and will be better for his next long term partner or the pattern will likely repeat.

thepariscrimefiles · 03/01/2026 16:09

Uricon2 · 03/01/2026 16:07

You've changed your tune a bit @Nicewoman

Your post on this thread at 4:41 this morning (one of many in a similar vein, some now deleted)

It’s not that, it’s why you think you can interfere & dictate who your adult almost 30-year old son can date? It’s like you’re stabbing him in the back & you will destroy all trust you have with him. Just so you can feel morally superior.
incidentally, the son’s gf probably doesn’t have a flattering opinion of you either before you start dreaming of buying wedding dresses & weddings in Tuscany. Foreign gf is wise to her flirty bf and has already planned her exit speech.

That poster has done so many screeching u-turns on this thread, my head is spinning. His early posts were incredibly rude to the OP and got deleted.

AmandaHoldensLips · 03/01/2026 16:09

I think he is lying to you about (1) only having downloaded the dating app that day and (2) the engagement ring.

He's clearly not unaccustomed to lying if he's a cheat, and I expect he's going for a damage-limitation strategy right now.

JHound · 03/01/2026 16:10

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.....

There is never a good reason to cheat

HelloDenise · 03/01/2026 16:11

PatsyJane · 03/01/2026 16:07

I think it was unreasonable not to warn your son you were coming home early. In fact I’m not sure this an actual true post tbh. Who wouldn’t warn family they were arriving unexpectedly at 11.30pm and then starts drinking and then asks son i his bedroom to go and get paracetamol and milk?
If it is all true i’d have pretended not to notice the woman and wouldn’t have questioned my son. It’s between him snd his girlfriend but now you know you know so you’ve put yourself in a difficult position.

If you think it's not "an actual true post" you should report it, not troll hunt. Why would someone make this up for fun, though?

ErsBears · 03/01/2026 16:11

PatsyJane · 03/01/2026 16:07

I think it was unreasonable not to warn your son you were coming home early. In fact I’m not sure this an actual true post tbh. Who wouldn’t warn family they were arriving unexpectedly at 11.30pm and then starts drinking and then asks son i his bedroom to go and get paracetamol and milk?
If it is all true i’d have pretended not to notice the woman and wouldn’t have questioned my son. It’s between him snd his girlfriend but now you know you know so you’ve put yourself in a difficult position.

I don’t announce to my DH if I’m coming home early either, it’s my house I can arrive and leave whenever I like without having to let anyone else know. I’m sure my son doesn’t let his flat mates know every time he is leaving or coming home.

We also didn’t start drinking when we got home, we went for a meal and drank then, I didn’t know we were out of milk etc. as I hadn’t been home in several days, DS managed to finish 2 litres of milk and all the cereal. I couldn’t have imagined he’d have a stranger over. I do not want strangers in my home, it’s my home! I only knocked as I could hear the tv and see the light was on under the door and he usually loves an excuse to go to the supermarket at night.

I also wasn’t going to turn a blind eye to a stranger in my home as that’s not okay, you don’t bring extra guests to someone’s house without checking with the owner of the home, it’s common decency.

OP posts:
JHound · 03/01/2026 16:12

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.

As we see here - these are the women raising the men that women complain about. All morality goes out the window when it comes to their “Precious Son”.

Differentforgirls · 03/01/2026 16:14

PatsyJane · 03/01/2026 16:07

I think it was unreasonable not to warn your son you were coming home early. In fact I’m not sure this an actual true post tbh. Who wouldn’t warn family they were arriving unexpectedly at 11.30pm and then starts drinking and then asks son i his bedroom to go and get paracetamol and milk?
If it is all true i’d have pretended not to notice the woman and wouldn’t have questioned my son. It’s between him snd his girlfriend but now you know you know so you’ve put yourself in a difficult position.

Always a woman’s fault eh?

JHound · 03/01/2026 16:15

ErsBears · 03/01/2026 04:06

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!

This means he cheats on her regularly. She needs to be free of your son.

Anyahyacinth · 03/01/2026 16:15

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!

Couldn't live with myself if she built a life with someone who didnt care enough to be faithful, she has already wasted 2 years on this relationship. I think the moral choice is clear

shuggles · 03/01/2026 16:16

I'm in disbelief at the responses, and the number of people who are completely indifferent to a man having multiple sexual partners.

So is it actually an issue for a man to have multiple sexual partners? Does it suddenly become OK if the man is a relative, such as a son?

Perhaps cheating men are not the issue after all; the issue is the people who defend them.

JHound · 03/01/2026 16:17

ErsBears · 03/01/2026 04:06

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!

This makes it worse - he has a girlfriend and is on dating apps? He will be the kind of husband who continually cheats.

Notbridezilla · 03/01/2026 16:18

Having been the woman on the receiving end of a similar scenario, except that my ex’s mum knew about it and did nothing - thank you OP for being a decent person. OF COURSE it’s not ok and OF COURSE the gf needs to know. anyone who thinks there’s any excuse not to tell her has obviously never been in a situation where cheating was involved.

JHound · 03/01/2026 16:19

Bellavida99 · 03/01/2026 05:14

It’s really odd you didn’t message to say you were coming home early almost like you wanted to catch him out. He could’ve heard a noise and hit you over the head with something! I always let my kids know if we’re coming home early. I think it’s none of your business and he might be thinking of finishing with her but with the holiday booked might want to see how that goes. They’re not married or living together. While I agree he shouldn’t be cheating long term, the odd infidelity or overlap isn’t a huge thing. You not letting him know that you were coming home is the issue here

Jesus wept….

CutePixieGirl · 03/01/2026 16:20

Differentforgirls · 03/01/2026 15:49

Coming from you that’s rich considering you accused the mum of being too drunk to buy her own milk.

It’s evident that the whole family lacks respect.

No accusation required, it was written in the OP.

Bc87 · 03/01/2026 16:21

Jane143 · 03/01/2026 15:20

I’d stay out of it. Let him enjoy his imminent holiday and maybe if it goes well he will decide she’s the one. He’s young. Men don’t settle and marry so early nowadays. After the holiday is the time to talk. If you tell him today it will ruin a costly holiday for them both.

This can only be written by someone who has cheated.

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