has found a FB message from the woman he shagged in a loo cubicle - thus ending 1st marriage.
2nd wife is my sister (hence name change). She's bothered by the exchange, although it only said "hi how are u" and some inane chat about how she's into zumba now, not bothered enough to bring it up though. Says it pointless and she doesn't want to be seen as nagging or paranoid.
She asked what I would do, I think I'd overreact horribly say something but not sure what to suggest...