X (aka SJB/Nicolas) is an exclusive male character in CrossFire China.
The character model appears to be based on a player who won a contest in CF China. One of the rewards of winning this contest was getting a character in-game which looks like you. The GR vside wears a dark blue suit with black leather shoes; however, the BL side has a vest with a red shirt and is wearing sun-glasses. The character's archetype is a Chinese HongKong actor, Nicholas Tse.
Just like G.E.M, in 2013 Nicholas Tse became the first endorser of CF China (The second is Gloria Tang), also, he create a song for CF China in same year; however, SJB doesn't have exclusive voice pack like G.E.M.