Honestly, your wife and her siblings should be ashamed of themselves, enabling him all these years, he is now 65 and doesn't have enough time to change into a better life. Maybe he never would have but they will never know as he was always coddled and taken care of by his siblings.
At this point they should take care of him as he's never been taught to take care of himself.
It's tough to say no to family but at times it needs to be done.
If it's any consolation you're not alone, My BIL is a worthless piece of schit as well. My wife jumped on board with me when he stole from us, his mother kept enabling him even as he robbed her blind. He'll never change but at least his mother finally did at my daughters urging.
About the size of it.
