What should I do in this situation?

[david b]

While I must say your brother sounds like he has some issues, being a liar is one of them. Just bare in mind what you now know about him for future reference.

On a separate issue is this. What you did was in fact was an invasion of your brother's privacy. He was certainly careless to leave that page opened for you to see. That is no excuse however. Doing what you did almost always ends up badly. I would suggest the next time an opportunity like this presents itself, that you resist the temptation.

To answer your last question, you shouldn't DO anything about it. The truth has a way of working itself in to the light with out any help at all!