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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

To blow everyone’s world up

337 replies

Secretspiller · 03/09/2019 20:23

Name change for this one

My SIL and I are very close, best friends. My DB is a pain but I love him. They have 4 children. She confided in me at the weekend that she had her second affair last year, this time with our mutual best friends DP. They have 3 children.

The reason she told me is someone else knows and is using it against her so she wants me to back her up if/when it comes out.

DB suspected last year and we all told him he was mad. She would never do that again as she nearly lost it all last time. I sat and listened to her for hours about how DB was making her life miserable with these accusations, he was right with the timing and the person.

The man in question is a sleaze, always has been and I long suspected he had cheated on best friend many a time. If it comes out, which it will do, that I knew (after the fact) I run the risk of losing DB and best friend. If I tell I lose my SIL who is also my best friend and blow up 2 very interconnected families and a wider friendship group.

It’s over and has been for a while, he’s moved onto SIL other friend who is not really in the group. Despite the fact best friend thinks they are trying for another child.

I want to tell. I’m dammed if I do and I’m dammed if I don’t. I wish she hadn’t told me!

OP posts:
WhoWants2Know · 03/09/2019 21:43

I would pick up a new SIM card, slip it in my phone and send a text to your brother and best friend, explaining the situation. Then switch back to your regular sim and no one knows it was you.

Lplus2 · 03/09/2019 21:44

How would you feel if your husband was cheating on you...not once but TWICE and your brother knew and said nothing???
Really think about that.

I’m sorry but your SIL isn’t your best friend to put you in this situation yet again.
This will just continue. Also are you willing to lose other family members over this? They will pick sides when this comes out and knowing you knew may cut you out also, regardless of it being right or wrong it will happen.

If your SIL is so unhappy tell her to get a divorce then she can sleep with whoever she wants.

ReanimatedSGB · 03/09/2019 21:47

How absolutely horrible for you, OP. I normally advocate staying out of other people's monogamism issues because it never ends well, but in this case I think I would be saying to her, this is my brother, either you tell him or I will.

saffy1234 · 03/09/2019 21:48

This can't be real are people actually this promiscuous and vile Shock

saffy1234 · 03/09/2019 21:50

And OP your SIL is clearly a bit lose that why shes 'done this' ,again might i add

saffy1234 · 03/09/2019 21:51

Loose even

dontdoubtyourself · 03/09/2019 21:53

Your brother thinks he's going mad and you've told him he is and you think it's OK to keep it from him? He deserves the truth for his own mental health. You stand by him not her. How can you even question that. She's put it all at risk. No one else.

Lyingonthesofainthedark · 03/09/2019 21:54

I'm shocked you colluded with your sil against telling him last year, and gaslighted him that he was mad. That's really not on.

ElektraUnchained · 03/09/2019 21:55

Good lick with your brother. She is an arse to put you in this situation and you don't owe her any loyalty.

PumpkinPie2016 · 03/09/2019 21:57

I think you have to tell your brother and the woman whose husband is/was cheating.

It's never going to be easy but imo far better they hear it first hand from you then find out some other way (and they will!) and then find out you knew about it.

She has done this twice, the man she has cheated with has obviously done it more than once as well. Both your brother and your other friend deserve better.

IamtheOA · 03/09/2019 21:58

I'd tell her she has 2 days to tell him herself or you will and that she has put you in a shit position

Yes

And, as pp said....this woman has no morals or loyalty- she WILL fuck you over, it's only a matter of time

DieBabySharkDie · 03/09/2019 21:59

.

HollowTalk · 03/09/2019 22:01

You have two friends. You can only keep one.

Do you keep the one who's cheated on your brother twice, and who thinks so little of you that she expects you to lie to him and your other friend?

Or do you keep the woman who's been cheated on, who's married to a bastard, who needs every help she can get?

Your SIL might be good fun on a night out, but as sure as anything she's not your friend. She is using her to protect herself, at your own brother's cost.

Actionhasmagic · 03/09/2019 22:04

Tell!!!

pappajonessecretchild · 03/09/2019 22:04

this is not the first affair? she isnt in the relationship with your brother as a long term commitment. you run the risk of loosing his trust, and also the rest of your family when they find out you knew and didnt say. I would see him asap, tell him he was right. tell him everything she has said and asked of you. then go and see the other friend. i wouldnt waste time even replying to her, the lack of reply today from you will have her stewing anyway, and the first thing she will say is that you knew to deflect some of the deceit of her. Get in first, stay factual of what she said and just keep telling your brother that you wish you had taken him seriously last time as he was right.

ssd · 03/09/2019 22:04

She sounds like a piece of work.
I'd keep well back.
She's not your best friend, she's a liar and a user and needs a boot up the arse.

fargo123 · 03/09/2019 22:06

The fact you colluded with a disgusting cheater against your own sibling says a lot about you, too.

Kaddm · 03/09/2019 22:08

What a mess.

You’ll have to go with what you think.

Ordinarily I’d say stick by your brother. However you say he’s a pain and I’m wondering how much of a pain and what he’s done.

BringTheBounceBack · 03/09/2019 22:08

there is nothing to justify this woman’s behaviour - so why are you backing it? Why are you allowing this to happen to your brother?

MaryPopppins · 03/09/2019 22:09

It's really really unfair that she has put this all on you when you've done nothing wrong.

Really cruel.

I agree with others saying tell her she has to tell them or you're going to. And you won't cover for her.

BoomyBooms · 03/09/2019 22:10

She's cheated, twice- she's in the wrong, so if you support her in this you are taking the side of the wrongdoer. Your DB and other best friend will value your support in this.

Don't leave SIL alone with your partner!! Sounds like she'd screw you over in a second.

GodDammitAmy · 03/09/2019 22:10

It's going to come out an`anyway OP, your SIL has told you that. It's a horrible position to be in, I've been there and kept quiet. It all came out in the end and the adulterer changed the narrative to make herself the victim. I somehow ended up as the bad guy. It was a mess. You have to do the right thing by your DB and BF. Good luck Flowers

INeedAFlerken · 03/09/2019 22:12

I'm glad you're telling your brother.

SIL is awful for cheating on him in this manner, continually lying about it, and now demanding you do. He's your brpther!

Good luck.

AlpacaGoodnight · 03/09/2019 22:13

Good luck, you are doing the right thing. Any fallout is not your fault.

TheABC · 03/09/2019 22:13

Reverse it. How would you feel if your brother found out about your DP cheating...and did not tell you?

I would also tell the best friend, if only because she needs to halt TTC with that sleezy fucker of a DP before he leaves her, holding the baby.