Look, I've seen all sorts of arrangements, so I'm not going to judge.
However, when the SIL starts mouthing off about her husband's interest in porn, it took things to a whole new level. That was highly inappropriate.
Wife #1, Satan, used to pull tricks like that. Porn was never an issue. However, she'd wait until we were all gathered for a family event like Thanksgiving and then make some horrible accusation or dredge up some dreck from the deep past and try to make it the center of the event. Usually, this was due to her predilection for control and she used these events to punish me. My folks got wise to this really quick and started discounting her and the accusations. The truth of it is, growing up a good Methodist boy, I had been completely honest with my folks about just about everything, so nothing really surprised them. That's a good thing to remember, folks. Honesty IS the best policy. When she started making stuff up out of whole cloth, my family knew it was hooey.
This all escalated until she realized she wasn't getting any traction with my family, so she started trying it with others. Finally, she called the police one time and that sparked the end to the marriage. I won't go into details, but she was probably trying to get me killed.
1) This is the first shot across the bow of a really malignant situation.
2) Once this kind of crap starts flying, I see very little hope of this marriage being recovered.
3) If I were the BIL, I'd make an escape as soon as I could.
