very uncomfortable with somebody on a very beneficial group you're in?

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I'm committed on a very beneficial group for my professional practice yet i feel very uncomfortable with one of our members. i suspected him competing on my works and the other members' works every time. and the suspicion seems to be right. i didn't mind once but now he seem to try very hard to be better than us. he act so knowledgeable at all times, especially during conversations seem new to him, and push his self before us. now he seem to boast by his achievements knowing that he improved much. i guess I'm just jealous... but my suspicions and the way he act both impose it right. i love the group and the members but the situation is making me to pull back a bit. what should i do? what are your insights about this?