This post is shocking. I can’t understand why you would invade anyone’s privacy. If your brother wanted to know, this is something he should have done. I don’t see this being any of your business. Your big brother is a grown man and needs to handle his own affairs.
Something like this could blow up in your face. You are just out of line and have your nose some place it doesn’t belong. Shame on you. I hope your sister in law have the opportunity to know that you overstepped your bounds.
What do you mean can we win. There is no winning for either sides in divorce. Perhaps one may get out of paying money or losing property but both people ultimately loses. Don’t encourage your brother to possibly lose everthing as a result of your inappropriate behavior. Just because he told you NO, there is always two sides to every story. I know you think you are helping your brother but believe me, things like this always end up blowing up in a ugly way.
I hope all works out well for both and they are allowed happiness again in another relationship.
Try to stay neutral.