Marty had been more than content not to share - it was one thing for the people he considered family to know, and though Marty hadn't really said much of anything to Morgan the man had to have at least some sort of vague idea about what Marty could do. If not exactly what he could do, then at least the knowledge that his power involved the mind at the very least. Morgan wasn't stupid after all.
Of course his plan on not saying anything worked right up until the point that Morgan came in and announced to the group that apparently Marty was an empath. Marty resisted the urge to whip his head in Callen's direction and give him a look, and more than that he had to resist the urge to push right into Morgan's mind and find out what it was the two of them had talked about that ended up with Morgan giving Marty a power that wasn't his.
The temptation was difficult but Marty managed it, it wasn't the first time he'd had to resist such a temptation, though perhaps this was the time when Marty was most sure he could get away with it unknown to anyone. Of course then he'd know and for all that Marty hadn't ever considered him a good person he did try to act like it.
"Don't worry though, just because I might know how you're feeling doesn't mean I'm going to make an invitation for you to have a heart to heart." He assured everyone with a slight grin. He supposed it was better than telling people about his real power.
Tim was scowling at Morgan, arms crossed over his chest, but didn't feel the need to crack a joke about his freak power or his comic book counterpart. In fact he was more than happy to keep right on not saying anything to anyone. They could figure this out without him or his power.