I used to be able to screen share with my cousin using Messages. It is now broken. What does he need on his end to get screensharing to work again? I have an AIM account setup in Messages on my Mac running the latest version of Mavericks. He has the same setup on his Mac. He doesn't have an AIM account, just an iCloud account. Does he need an AIM account, too?
He is logged into Messages with his iCloud account, but the screensharing option is dimmed and I cannot ask him to share his screen.