Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
youngster [ˈjʌŋstər] n молодо́й челове́к#; (child) ребёнок#
the youngsters of today сего́дняшняя молодёжь
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.