Is OTHER wrong in the post ? POST : Ok, so I (M 22) find myself in this weird situation. Kind of immoral I guess. 
I got two friends, one girl and one guy. They recently broke up (they had a hard time with each other for a couple of months). Let's call the girl Jane and the boy Joe, both aged 21-23. 

The situation: Joe had an affair with another girl for a long period of time. That's the reason he broke up with Jane. The thing is, Jane doesn't know this. She believes he broke up because they grew apart, and is having a hard time understanding this. 
Joe told me the entire story of his affair, but doesn't want me to let Jane know it. 

Me and Joe are good friends. Me and Jane are good friends... Really good recently.
Joe is not treating Jane's pleas well of having talks, etc. post breakup. It's making her frustrated because she doesn't know the reason for it, but she just wants to move on. She is telling me that "if he just had an affair it would be much easier"... 

Joe and the girl from the affair is starting to form a couple now, secretly. Because they don't want Jane to know to fast. I, as a good friend of Jane, is wanting her to know because I want her to be able to move on and be happy.

The question is: Am I the asshole if tell Jane that Joe had an affair? 