So as you may be aware, Mr. Ivriniel has an annoying brother. That annoying brother has an annoying wife. Also, my Father-in-Law is highly opinionated and extremely judgemental, very stubborn and quick to take offense.
This is none too surprisingly, not a recipe for family harmony. It often leaves poor Mr. Ivriniel as the the only person still actively talking to all the various factions of the family.
A few years ago, he managed to broker something of a peace between his sister and his Dad. They aren't close, but will tolerate being in the same room as each other now, and my FiL now gets to see his granddaughters. It was not easy, and Mr. Ivriniel pretty much had to manipulate his Dad into it. As Mr. Ivriniel puts it, his Dad is so ornery, that if you tell him what it is you want him to do, he will just refuse to do it.
So now, ABiL wants Mr. Ivriniel to try and work magic again, and clear the air between his family and my FiL. This is not going to be easy. The two groups are really passive aggressive towards each other and have a long memory for slights. Two Christmases ago, FiL gave ABiL some sort of self-help book (FiL is big on giving self-help books as gifts. He thinks he knows how everyone should live their lives.) So to push back, ABiL and ASiL gave FiL something to the effect of "Family Relationships for Dummies" for this past Christmas.
I have no idea how he will even approach this. My Sweetie has the patience of Job.