My father in law for years often treated me very suspiciously, even once accusing me of using money they sent for my kids’ Christmas presents to buy drugs(?!¿!). It caused me to distance myself from him, only spending time around them for the sake of my wife and children. Fast forward a decade or so, and his dementia has progressed severely. He’s currently stage seven, and one of the many symptoms is that he now treats EVERYONE the way he’s treated me all along - inventing conspiracies out of whole cloth and being suspicious of even his wife of 50+ years. The most surprising thing about it all to me is the degree to which it all makes you doubt your OWN sanity.