Need advice.

My boyfriend and I have been together for a year now and I'm incredibly happy,  now I've known my best friend for years now and we'll heres where it gets complicated. I get completely jealous when they're together just talking or messing around. I just don't like it. I understand it's nothing wrong because in general they're just really kind people but I can't seem to find peace in this. What can I do to avoid feeling this way without getting them both involved.