They never cared for me and didn't want their son to marry me, but we were 40, so he did as he pleased. I've had a cordial relationship with them for 20 years until this past spring. After celebrating my birthday, they fabricated an "insult" and have refused to see or speak to me. My husband and teen son have tried to reason with them, even prove they are mistaken, but it's no use. My FIL forced us to remove bins we had in storage in the attic, berated my husband for every perceived transgression going back 40 years, including marrying me and will no longer see him either. He's also called me terrible names to our son and completely fabricated incidents involving me and passed these stories to extended family. I don't think they have dementia but my FIL has had a couple of strokes.
The whole family is in upset. I've never experienced people at end of life who have purposely blown up a family like this. My husband has 3 siblings and they will not intervene because they're afraid my FIL will turn on them as well. Separately, they say he speaks badly of everyone, punctuated with a self-congratulatory, "I remember," with every recount, as proof he still is mentally fit.
At this point, I can ignore them. But this is killing my husband, who has always been close to his mom, at least. And it's upsetting our son who's always seen them as loving grandparents. Would appreciate any advice.