better to stay out of it, it's just going to look like you are trying to break them up. Let his best friend tell him.
but you still need to respect his bounderies and that isn't.
It could be a set up. I would not say anything unless you and your ex are on excellent terms.
Too much drama, stay out of it and mind your own business
Don't get involved. This can't end well.
Yes. it is never good to hide something like this that you know. But then again they could think you are just saying this to break them and that person up. But it is always good to be honest with someone about something especially when you know what's going on.
The truth will reveal it self sooner or later just be patient ! And u never know if ur friend is lying o.o If u do tell him its going to seem like ur jealous and u want to break them off. Unless of course he trusts u