Your wife knows how much it pains you when she spends the night with other men, and thoughtfully gives you the choice of her telling you, or not telling you, exactly who she’s going to be having sex with. So far, she’s been with a couple of men from her office and a number of guys she met at her gym, but – as far as you know – this will be the first time she’ll be having sex with someone you know. That thought sends shivers down you spine, and you realize she is right that as painful as tonight will be for you, it is probably better that you don’t find out exactly who she’ll be with.
Your wife's sister knows how small you are, and has been trying to get your wife to date her boyfriend's brother for ages. And now your sister doesn't feel she can say no -- since she wouldn't want to turn down such a generous birthday present from her sister.
This is totally true. My wife started dating other men during a time I was traveling a lot for work and she would usually call me before and after each date.