OP here. As disheartening as this is, I thought I should update this thread.
So, today's social gathering. One of the girls there has grown extremely fond of him. She's two years older than him, so I thought it was more of a sisterly thing before, but now... Lots of unnecessary touching, joking around, always sitting next to each other... it was blatant today. Someone even speculated they might be dating behind the scenes.
To be frank I'm insanely jealous but what can I do about it? He's still perfectly friendly to me, and though I think he's equally friendly to her she definitely seems to have something for him.
I'm crushed, to be honest. Maybe I'm better off just forgetting this guy. He plays too hard to get, and now I've got competition?? Maybe it's not worth this much effort. Thoughts?