It depends on what you want to say-- if you mean little brother like most people do, as in younger brother, than it's NOT маленький брат (malenkiy brat-- stress on "mal"). It's младший брат (mladshiy brat-- stress on "mlad"). Маленький брат means small brother, as in physically small, and isn't really said in Russian. That's what happens when you use computers to translate things. You could possibly also say братишка (bratishka-- stress on the "ish"), which is a dimunitive form of брат (brat)-- the word for brother.
