A short bio, that was omitted from final version of S.T.A.L.K.E.R.: Shadow of Chernobyl game describes him as follows: 
Klutz is 20 years old. He lost everything and everyone in the Big Land before deciding to come here. He barely makes a living in the Zone, but he simply has no other place to go to. Owes money to many stalkers. Frequents the Zone, but never goes there alone. Always trying to hang on to a group of experienced stalkers. Not a popular companion, as more often than not, he's plain useless. Hardly makes any money. Lives on doles from other stalkers and is deep in debt.
↑S.T.A.L.K.E.R.: Shadow of Chernobyl; stable_bio_name.xml