Let him spend his time in more meaningful activities so that he
wont have time for computer and gradually when that becomes a hobby
he will play lesser and lesser in computer games until it becomes
zero gaming activity.
My brother also has the same problem lah, but this one is even
worse lah, play more than 12 hours a day, morning wake up, walk out
my room is see he playing liao, then go out and come back at night
still playing. haha, well i have tried all i can, now i m just
gonna let him have a taste of his own failure in his studies.
Man, so u must bring ur brother out more, go exercise, jogging, go
church, go out to do things that are more meaningful that's it.
Fill his schedule with tuition, music lessons and outings. And i
think that's gonna be fine.
Hope it helps. 
