četvorica

1. (of men) four men; four of them
   Nas četvorica idemo na pecanje u subotu. — The four of us are going fishing on Saturday.
   Videla sam četvoricu policajaca ispred zgrade. — I saw four policemen in front of the building.

Takes the genitive plural and refers to male persons, including boys; for mixed groups or children without specifying their sex, use četvoro.