Should I tell my sister's boyfriend that she's cheating on him (with her ex)?

[Anonymous]

A little background: I'm 18 and my sister is 21. She has been in a relationship with her current boyfriend for about 6 months. She lives with him about 20 minutes from home.

What he doesn't know, is that whenever she comes home to visit, she spends most of the time with her ex boyfriend.

Last Friday, I caught her and her ex "fooling around". I feel bad for her boyfriend, and very guilty for not saying something. I've been thinking of messaging him to inform him. Should I? If so, how should I go about it?

I've never had to deal with this type of situation, so I welcome all insights, advice and questions.

How would you feel if your girlfriend's younger sister told you about her affair?

Updates

+1 y

I appreciate all of your opinions.
I will continue to think on it and figure out the best way to approach the situation. Thank you all for the honest advice! It has definitely helped.

[hellionthesagereborn]

Yes you should, he has every right to know and what your sister is doing is really shitty. Just give him a text or send a message and go from their, if he choose not to believe you then that's fine its his choice. I would also confront your sister about it because again, its a scummy thing to do and just as you wouldn't want this done to you and living oblivious to the fact I think its only fair you notify him.

[nosweat2012]

If he's a nice guy then it's pretty sad for this to happen to him. in my opinion you should confront your sister and tell her to break up with the poor guy or you will tell him. It will be painful for him either way but better it ends now than he stays around getting cheated on

[Asker]

This makes sense and it seems like the right thing to do. How do you suggest I confront her if we've already argued, and her and my mother have since kicked me out? I don't have any way to contact her and don't really want to anyway.
Very good advice! I just have no clue how to execute it.

[nosweat2012]

Sorry for the very late reply. That's pretty tough.. If your mum has sided with her I dunno how you would go about this. Unfortunately from what you've told me here it sounds lime it would be best to leave it. Far from ideal, but best. You dont want to stress yourself out even more even if it is helping the guy. Sorry, I'm just really unsure

[ruzzell]

I think you should coz its unfair to the poor guy... even though it will coz to make your sister get mad at you its still the right thing to do... Or confront your sister about her wrong doing... And just be honest to his current boyfriend

[Mekara]

Put yourself in his shoes. If someone knew your SO was cheating on you, would you want to know? If it was me, I'd tell him. Cheating is the worst thing that could happen to someone. No reason to keep the guy in the dark about it.

[azzntittiz]

A lot of people here will say you have a moral obligation to do so but it's really none of your business. People cheat and once why they do it and the repercussions won't affect you, it's not your business.

[rico99]

doesn't change the fact its wrong and he deserves to know.

[azzntittiz]

@rico99 Doesn't change the fact that you could just stop snooping around people's private parts and lives.

[rico99]

The right thing to do is let him know the truth period.

[azzntittiz]

@rico99 Like the period in my pants now? :/

[rico99]

Wow no like at the end of a sentence

[smcv21]

Yeah, you should definitely tell him. There's no point in letting your sister continuing to do that to him. He deserves to know.
If you are in contact with him on Facebook or something, you can message him there and be honest with him, tell him what you know.
If you want to do it face to face, just be straight up and be blunt with him.
Depending on what you want to do, you could have sex with him or send him some sexy pics of yourself. He'll be wanting revenge, so this would be the best way to help him out.

[Idontknow012]

First talk to your sister and tell her that is not correct, and its a slut behave.

If she don´t care, just let the things going because if you say something to her boyfriend he might think you want something with him, or even try to have something with you to make your sister jeluse and you can have problem with your sister

[BornUnlucky]

Wow. That's a tough situation.

Here are some things I would do.

If I'm unsure I would ask my sister. Ask her why she's cheating on him, and why she's still with him.

If I knew I was telling him I would do so anonymously. Unfortunately for you it's possible she knows you know and believes you're the only person that knows or that would tell him. That's potentially a family splitting thing. In her eyes it'd be your fault her relationship ended because you went behind her back.

I think I would give her two chances to stop or tell him herself. After then I'd say I told you so and tell him.

[madhatters4]

i would tell her that she needs to come clean and that if she doesn't you feel like you may have to tell her boyfriend what's going on

it gives her the power to do the right thing but also makes it clear that if she doesn't do the right thing you will

[Prakbio]

why you want to tell him?
is he is your good friend?
do you have crush on him?
do you her ex know she is having new boyfriend?
anyways she is your sister you have to live with her when she came to knew that you told him about you. you will have bitterness in your relationship.
instead of telling him try to make your sister understand that this is bad what could be consequences of this type of relationship.

[ir0nc1ad]

My advice is to tell him.. it may cause some problems between you and your sister. But it's not fair to him that he's tied down in commitment and she's fooling around..

[Alistayr]

If someone did that to me, I'd want to know, but it could cause a big disagreement in your home. Have a word with your parents, and see how they feel about it, and take it from there.

[Michaeljoh13]

You should make a plan, wherein your sister's current boyfriend catches her with ex.. As she does it

[Michaeljoh13]

Whenever your sister meet her ex outside, just tell him the situation so that he catches her red-handed. And you played a safe game

[Asker]

This is very similar to my first idea. I was planning on messaging him, letting him know, and telling him show up without notifying her.
I was also going to ask him not let her know I informed him to keep it civil; and instead say he figured it out himself, or that one of his friends told him.
Is this a good way to go about it or does it seem to dishonest?

[stawrman]

Tell him to come under the excuse of a surprise, that way it's absolutely fine

[Manuel2]

If you have not sin, then tell. I think you like her boyfriend and want to find away to break them up.
It would be nicr to expose your sister as a cheat (with evidence) but once exposed a SLUT? than cheater, men will only use her as a walking sperm bank.
Do you love him that much to hurt your sister that much

[rico99]

The hussy is doing it to herself. This 18 year old lady should be made to feel bad for wanting to out her slutty sister for being a whore.😤😤😤😤

[rico99]

Should not be (correction)

[Moekay]

No, stay out of it. If she finds out you told him she will hate you for it for the rest of her life. I feel bad for him too.

[Asker]

The funny thing is: she already hates me for catching her lol. I've since cut her off as I've been kicked out over the ordeal. I feel that since I have nothing to lose, I should go all in, if that makes sense.

[Moekay]

Even if you and your sister don't like each other and telling her boyfriend does sound like the right thing to do. But its your sister and going to be your sister forever. Not worth it.

[Asker]

I appreciate your honesty

[rico99]

Take a pic of them in the act and tell him. Your sister is doing something unforgivable. He deserves to know and unfortunately your sister deserves some single life live if she (i apologize for my next choose of words) gonna act like dirty nasty whore behind her boyfriends back. And you can tell her i said that she is acting like a tramp.(sorry sweetie but cheating is for those who deserve loneliness)

[Anonymous]

No, that's your sister business and it has nothing to do with you so let it be and maybe if you do tell her boyfriend that your sister will think differently about you and your relationship may become a little unhealthy and she will no longer trust you.

[Asker]

We already got into a spat about it, which somehow led to me being kicked out of my home; that she no longer lives in.
We've always had a rocky relationship in which she mentally and emotionally abused me through manipulation, lies and violence.
I'm not afraid to lose her respect (which, by the way she treats me, never even existed).
Through the years I've lost trust in her and respct for her. This situation was only the last straw.
She's not a good person, and personally i think it would be good for her to learn to respect people and relationships.
I feel as though me telling would be beneficial to everyone involved.

[DamnMan]

If he's not a friend, then I don't think so.
The only thing I'm worried about if he's the berserker boyfriend that will go crazy on a cheater.
Also, moving in after 6 months is a little fast, even for me.

[false]

next time you catch them "fooling around" just lowkey tell her boyfriend to come over and check this out

[morrigane]

i think u should tell her boyfriend

[Asker]

Do have an idea on how I should go about it?
The only way I can contact him is through messenger.

[morrigane]

tell him i have something to tell you face to face and when you meet with him just be honest there is no other way but known that ur doing the right thing

[Asker]

That sounds like a great idea.
The only problem I have with that, is me and him have barely talked, even when he visited, and I have bad social anxiety.
What if he thinks I "want something" from him?

[morrigane]

no tell him something really important and that you must meet him

[Anonymous]

It's simple. Use a friends phone and tell him through text. Make sure your sister doesn't know this friends number and their are no connections between the friend and your sister.
I feel bad for him and would tell him about it.

[rico99]

That is the best yet good answer

[sheajake17]

Poor guy. Tell him tho. But its better if u have evidence.

[Sammy1303]

Yes I have been cheated know before and it's better to find out from some one else then ur self

[noesbueno]

Yes. I would tell someone if they were being cheated on

[JenDB]

Talk to your sister make her think resonable. Do not betray her right away.