Earlier quoted context omitted.
Unfortunately they’re both terrible to each other. Always have been, likely always will be. Even in relatively stressless situations they end up at each other’s throats in seconds. The family (not my wife) asked me to talk to my brother-in-law about this because nobody else could get through to him. I totally agree I’m not the right person to get in the middle. There’s just nobody else willing or able to.
> The family (not my wife) asked me to talk to my brother-in-law about this because nobody else could get through to him. This is a very tough situation and I don't think it was any lack of skill on your part that made you unable to get through to your brother-in-law this time. I don't think the world's champion hostage negotiator could have done it on the first try. I'm a little unclear on one aspect, though. You sa…
A technicality: Not sure in the USA, but over here that's not correct. Relation is measured in grades being those the basic parent-child "distance". So you're related in the first grade to your parents or children, but in the second grade to your siblings (1 grade distance from you to your parents, another one from your parents to them) so, unless the father in law has a living parent, no one is more closely related to him than his children.
So for lack of a better way of understanding, I would just ask a lawyer.