I have been seeing my fwb for just shy of 3 yrs. Almost a year ago he told me he got a girlfriend. I told him I didn't want
To see him anymore. A few months went by and he contacted me again and said he and girlfriend having some problems. I told him if they were not a couple then I would see him. I continued to see him for the entire year he was dating his girlfriend without knowing. So I happen to find his girlfriend
Facebook profile and find out he is now engaged to her.
He still wants to continue this even after I told him I knew he was engaged. I of course said no that I would not see him.
He is still trying to get me to say yes to at least one more time,but he still wants it to stay the same.My question is should I message this girl that I don't know and tell her what he's doing and that I have proof or just let it go. I asked him why does he want to continue if he's getting married and he said he wasn't sure. Any advice and insight please

Act as if you were on her shoes. Would you want to know? You could be saving her a lot of pain in the long run. Do not settle for being a man's number 2.

Is none of your business, erase him number because you don't need someone like that in your life and move on. There are too many single people in this world to satisfy what you are looking for instead of being a potential home wrecker... why go into all that drama? NO need to tell his fiancé, she is a grown woman that will notice it with time.