How my little brother plays chess.

I am 9 years old. My dad loves chess. I love chess. My little brother seems to like chess, but its no fun playing him as he doesn't play properly. He calls the pawns pom-poms! And he always cheats and ends up winning because he moves the pieces however he wants. When he was younger, as soon as he could, he picked up the king and said "I won!" Although I tell him that the knights moves in an L shape and that the bishop moves diagonally, he doesn't listen and he then moves the pieces however he wants. He always says I'm playing the game wrong! I want to try to teach him to play chess properly and I'm sure he'll start playing chess correctly eventually.