Kevin, just so you know, I told my W's brother in an email about our situation. I told him to not tell their mother, but he did anyway. Needless to say, my W had quite the interesting vocabulary as a pre school teacher the next day when she spoke to me.
I did this stupid move right about the same time I first learned of Divorce Busting and the first responses on my initial thread were 2x4's which I deserved. My intention at the time was that I was hoping her brother could speak some sense into her. Instead it was more like I dropped a match into a can of gasoline.
I think your W just told your BIL what he wanted to hear to get him to drop it. Think of your BIL as a themometer with a faulty reading. And there is no way a themometer can fix a problem.