What is up with my bfs friend?

My boyfriend has this close friend who is engaged. He's been with this girl for a few years.
When we're out, I'll catch him starring at me and smiling. It's always when no one is paying attention. I don't really know what to do, so I'll direct my attention somewhere else. It's pretty awkward. We don't talk that much. I feel uncomfortable talking to him, so I don't want to say anything.
+1 y
It's becoming really often. I don't know if it's just to make me feel uncomfortable or something else. He's the guy that likes to annoy people, so I'm completely confused.
What is up with my bfs friend?
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