Ask him why he won't let Ты get one. And also; why do Ты want one so bad? Are Ты planning on posting Видео of Ты and your friends? Are Ты planning on posting AMVs Ты make...? или do Ты just want it to Комментарий on Видео and such?
First find out the reason why then try to come up with a compromise:maybe Ты could if he knows your Пароль and is allowed to check up on Ты или if Ты don't allow Комментарии on your videos.Luckily for me, I have an older brother who got one so I just brought that up when my parents сказал(-а) I couldn't (although all my Видео suck so I don't know why I bothered.-_-)
Why do Ты want a Youtube account? Is it because Ты want to make your own videos, или make Комментарии on other Youtube videos? или Избранное Видео that Ты like so Ты can watch them again and again? Maybe Ты should tell him why Ты want one. And ask him why he won't let you.