Dunno if this is bait, but in case it isn't:
Weightlifting should be started after the puberty's height growth has ended / is ending. Before that you can still train, just use your own bodyweight. He can do pull-ups, push-ups, abs and stuff like that, also cardio.
Weightlifting too early can cause stunted growth. You don't want your bro to be a manlet, do you?