How to restrict useage of downloaded content on an Xbox 360?

First off, let me start by saying that I really, really dislike freeloaders. Recently, I have purchased some DLC from the Xbox 360 Marketplace. Two Call of Duty Map Packs, 2 Halo Map Packs, and One Live Arcade Game. It totaled to about $50. I only then realized that my brothers, who have separate gamertags on the console, are able to access and use all of my DLC. Is there a way to block them from using it and make them have to buy it themselves?