Would you tell them about the affair?

[Rainbow]

More WWYD than AIBU.
DSis1 (married for 17 years) has been having an affair for the past 2 and a half years with a work colleague. He lives about 30 minutes away. She has tried to get my Aunt A and my cousin A to cover for her. Neither want to but she tells them after fact and BIL has never phoned to check, yet!. Aunt A cannot keep a secret so everyone in our family knows, DM, DF, DSs, DSis2, Aunt B, Aunt C, Uncle B, cousins. DNiece1 (20yo) suspects but doesn't know and is sounding people out "do you think my DM would have an affair?" Etc.
Do I say something before I slip up or just sit back and risk alienating DNs if they ever found out we knew and said nothing?

I think it's awful that none of you have told your brother in law. What an awful secret to keep. He deserves to know so he can choose what to do about his own happiness.

Tell your sister that everyone knows, that her daughter is asking questions, and she needs to sort herself out.

In your situation I would say something, but I'd tell sister first that I was going to do it if she didn't.

Thank goodness no-one will cover for her. I'm not sure that I would want to be the one to tell the BIL though.

My answer to the niece would be "why don't you ask her?"

"Tell your sister that everyone knows, that her daughter is asking questions, and she needs to sort herself out."

And do this ^^
And say that no-one wants to cover for her.

I think it's an awful situation for you all to be in. Your BIL may have suspissions, you don't know. I would talk to your sister and inform her of how her husband needs to know the truth from her before someone else tells him. If it was me, I would want to know if my husband was having an affair. The emotional damage it did me with my own suspisions was horrific and nearly broke me.

Tell your sister that everyone knows, that her daughter is asking questions, and she needs to sort herself out.

Yes, agree with this. It's only a matter of time, now.

Tell your sister that everyone knows, that her daughter is asking questions, and she needs to sort herself out.

Yup. This 100%

I would however give a time limit and say I’m telling BIL and DN if she’s not come clean.

I'm surprised if still is a secret from him if that many people know OP,are you sure he doesn't know and has decided to ignore it?
Has your dn asked you directly?
Speak to your dsis,explain about dn and her questions and ask her if she is prepared to tell her dd the truth,or make a decision to either be with the boyfriend,end it and stay married or become single and then tell dd what's been going on.
Good luck,it will all come out sooner than later whatever happens now.

Your poor BIL. Everyone talking and whispering behind his back what his wife happily sleeps with someone else for YEARS and she's quite content to let it be on everyone else.

How old are the other kids? Given the liklihood that he'd be expected to move out and see the kids as and when, is it possible he suspects but is s a red of losing his children if he pokes the nest?

@BernadetteRostankowskiWolowitz no one what to be the one to destroy him.
Although we all think he needs to know, it's the fall out, the effect on BIL and DNs that worries everyone.

@karmastar 99% sure. He is close to his DB and tells him everything. His DB is married to cousin. I asked her.
No DN hasn't asked directly. I could have dealt with that.

@1plus2equalstrouble other kids are 16, 12 and 9.

I don't have the greatest relationship with my Dsis but I think I need to find a way to talk to her. Maybe I'll get someone else to talk to her with me so she knows it's the truth. Thank you everyone