Middle Boy has EXTREMELY low self-confidence.  EXTREMELY LOW.

His method of coping with it is by showing off and being the "class clown".  It is to exaggerate his skills.

Things like "I am one of the BEST EVER in such and such video game" and "eleven random girls came up to me and asked for a hug today".

Somehow I need to talk to him about this without making his confidence lower.

Pray for wisdom in how to address this with him.  How people will still like him if he is just himself.