Sit down and have an "adult" conversation with your parents about your need for the Internet for school work, assuming that is actually your goal.
If you have a router that supports Gargoyle from HERE
that would be one solution that they could authorize only specific whitelist sites, but there are many other good solutions, for example completely blocking your addicted brother from Internet access with your current router configuration or dd-wrt firmware if that runs on your current router.
Explain to Mom and Dad that good parenting should guide them to find a way to tame him while not hurting everyone.
I would guess that a big part of the issue is educating parents, as they probably know little and just have to react by shutting it all down. My kids never had an technical advantage, at least until much later.