My sister is the OW and I’m not sure what to do

[Namechange420666]

Title says it all really, but I will provide some background information.
My sister is 35, I am 25. I am closer to my brothers, but when I was young she used to babysit me a lot and often took care of me (paid), so we are kind of close. Probably a bit closer than average siblings with a big age gap. I love my sister dearly, but she can be difficult. She’s always had this thing about me being the favourite and my dad never loved her, and sometimes I get a bit sick of hearing about it. Other than that she’s overall a nice person (well I thought she was, this is making me question it.)
Today I went to lunch with her. She seemed excited and happy which was great since she has been a bit down recently. She was telling me about her new boyfriend and all was good. I suggested she brings him to a party I’m hosting in June and then she told me she can’t because of who he is. Long story short he is someone who works for our brother who is married.
I don’t know his wife super well but I know her a bit. My SIL is pretty good friend with her as well.
I didn’t really dig around about how this happened or anything because I was in shock. I told her she needs to stop this before it’s too late (I actually think it’s already too late if I’m honest) and left. She has tried calling me but I don’t want to talk to her. I wish she had never told me. I also think it’s really fucked up because she seemed almost happy about it? I am really unsure what to do because while I am not friends with this woman, but I feel really bad for her. This is out of character for my sister, so out of character that part of me wondered if she is having some kind of mental health episode? But I think that’s probably just me trying to make excuses for her. I also don’t want my SIL to hate me when/if this all comes out because I really like her.
The only other person I’ve told is my partner, and to be honest I didn’t really want to tell him I just ended up telling him because when I came home he knew something was wrong. He says I should stay out of it and that I should just wash my hands of my sister for a while at least.
I kind of just need to vent because I’m freaking out but if anyone has any advice I would really appreciate it.

It's not really any of your business. She's still your sister.

She's happy and excited because she loves him or thinks she does. It'll probably get messy and it's likely she and others may get hurt, but you can't live her life for her.

I'd maintain your relationship with her, but just ask not to discuss that part of her life if she brings it up again.

Agree with @category12 — our friends and relatives make all kinds of unwise relationship decisions, which we’re not obliged to approve. All we can do is express our reservations clearly, and be there if/when it all falls asunder.

Oh god please stop being so judgemental, you will push her away. Just explain that you don't agree with what she's doing but you still love her. Yes she should finish it but she has probably been strung along by his made up woe is me stories.

Mind your own business. If you feel that it's so out of character for your sister that it's indicative of a problem, be supportive and check that she's ok. Otherwise, beak out.

Do you think she's told you thinking you will tell your sil and this will force the man's hand and she's hoping he'll leave for her/get thrown out and be forced to be with her?

This won’t be popular, but I’d tell your brother because it’s going to blow up at his business.

I'd be judgemental too if it was my sister! It's a rotten way to behave.

@Namechange420666 I don't think there's anything you can do. She shouldn't have told you and put you in this position. Keep in touch with her - love the sinner hate the sin kind of thing. She will need you when it all kicks off - and it will. Don't tell another soul what you know.

She isn't a bad person or having a mh crisis, the man is just as much to blame for this situation. Is she lonely, does he treat her well and she's a bit besotted. I wouldn't wash my hands of her, you don't know what's going on is his marriage. I'd just keep telling her someone, probably her and the wife, are going to get seriously hurt and it should stop. Does your brother know,

I don’t know. To be honest I don’t know why she told me because she knows I am a really anxious person. I cannot fathom why she chose to tell me other than I’m her sister so she knows I love her?

I think your DP has it right more or less. Stay well out of it. And it really has nothing to do with your brother either.

You can think about it to your heart's content but that's as far as it should go.

I didn't read further than the title.

Just tell her you don't want to hear any more about her situation, and then refuse to discuss it.

As others have said MYOB, she's an adult.

This is a bit more complicated than just 'mind your own business'. Your sister has clearly never heard the phrase 'don't shit on your own doorstep' as she appears to be simultaneously shitting on about three different doorsteps. She's having an affair with her brother's employee. Her SIL is friends with the man's wife. When this all comes out there will be repercussions and recriminations all over the place.

OP, I would tell your sister that you don't want to know any more about this affair. She's trying to drag you into what promises to be an unholy mess. Your DP is right, you need to wash your hands of your sister for now. She told you because she wants the attention and she doesn't care if it upsets you or leaves you with divided loyalties. Under no circumstances allow her to hoover you into it by saying you're the only one she can talk to about it.

A very stressful and unpleasant situation.

No my brother definitely does not know. I also want to say I know this is more the guys fault, my sister isn’t married and he is. But he wasn’t the one gleefully telling me over fish and chips. I do think he’s spinning her the normal poor me my wife is (cold/mean/evil/won’t shag me/doesn’t love me).

In theory this is totally correct... but in the real world if others find out that op knew and kept it quiet they may react badly to that, including others that op cares about.

Op personally I'd tell your sister that whatever she does is up to her and you love her no matter what, but that you can't support her decision to harm another woman in this way and that this could cause serious issues for your brother and sil and his business. I'd tell her that she can't speak to you any more about it while it's going on but you'll be there for her for support if it comes to an end no matter the circumstances but that you'd strongly encourage her to end it, if not for his wife then for your brother and sil because it could put a big strain on his business and possibly their marriage. Then distance yourself as much as possible.

Obviously she’s not trying to hide it as she’s blabbed to you, knowing MM has a family connection to yours and has now made it your business. You can’t unknow what she’s told you.

As MM is an employee of your brother’s and shagging his sister, I’d tell your brother so he’s aware and decide what to do from there, whether that’s your brother telling him he knows and/or SIL speaking to his wife.

I don’t agree with other people colluding in affairs by not warning the betrayed spouse who is unknowingly living a lie not aware that their partner is deceiving and lying to them and potentially passing STDs onto them. It’s nasty and cowardly.

I’d ask those people if the situation was not an affair but someone being cheated financially or entering into situation where they were going to be ripped off or be physically assaulted or robbed, would they warn them then or just let it play out? Not much different in it really.

It's not the brother's business either. He's the employer, not the guy's owner. Seriously overstepping to start interfering in his personal life.

Everybody getting involved is not going to make things better for anybody.

Do not tell your brother - it’s no business of his what his employees do in their private lives. Your partner is right - think you need to stay out of it.

@Namechange420666 How did they meet? Does your sister also work for your brother? Or spend time there?

Don’t know. My sister doesn’t work for my brother, but she has catered events for them and stuff like that so I am guessing Christmas party or something like that.

My best mate is the OW. I've told her I don't agree but she's still my friend and her relationship doesn't interfere with our friendship.

Yes the MM holds the most blame but it's still
not particularly great what your sister is doing and I feel sorry for the wife of the MM and any children he has. I agree with your husband OP about keeping away from her for a while. I would feel massively morally conflicted especially as it's your brothers company and his wife is friends with the MM's wife

I would tell her what she was doing was morally wrong, hugely unkind but, more importantly, terribly bad for HER. She deserves more than being some sad bastards ego boost and shady bit on the side. I would also tell your brother because as pp said, she is literally shitting on her own doorstep and that never ends well, for anyone.

Did she describe him as someone who works for your brother?

It’s really a shitty thing to do to your brother, also.

Interesting that she didn'tfeel good enough in the family either. Now she doesn't feel good enough to shut this down. Dont judge her. You were the favourite? You were raised to feel valuable? I think sometimes older siblings remember tougher times (financially) than their younger siblings.
I had one short relationship with a Married man in my 20s. I was so lonely and exhausted from waiting and hope that so.ebody would like me. I shut it down when I saw him for who he was. I had envied his wife. When I understood he was a predatory, entitled, user, that burst my bubble.
Maybe if you asked him "are you going to leave your wife?" he'll panic and end it.
At which point tell her she can do better. Don't shame her. Shame lowers self esteem.

She said his name, and I said “not (full name) who does (his job title)?” Because frankly I was hoping it was just someone with the same name. I didn’t really probe a lot after that I just stopped listening and my mind started spiralling and then I told her I need to go home. I am pretty sure they will have met at some kind of event she catered, probably the Christmas party as that lines up time wise. It is a really shitty thing to do to him and that’s a big part of what’s stressing me because he does a lot for her.