Shit like that happens. When my grandad died, my mother´s brother had not been committed enough, to say it somehow. My grandad trusted my father, his son in law, much better when taking care of issues as his condition worsened, and it became a rather unconfortable situation. After he passed away, my uncle at least had the decency to acknowledge his wrongs, and was thankful that my father never tried to take any advantage of the situation.
Either way, fuck your bro-in-law. I strongly suggest you not to rage up, and show restrain in the sense of not comprmising your wife. Just support her in whatever she needs, and be prepared to take a lot of unfair shit, because in the end, taking care of yours is much more important. If you should come up to the funeral and burial, and whatever other issues may follow, remember that it is not the time to get mad with your family in the line of fire, no matter how right you might be. Just damage control man.