Dear Fed Up,
It's not easy sharing a room, and sharing it with a 2-year-old may be the hardest situation of all. Kids of that age don't mess up things intentionally—they're just naturally curious. And they haven't yet learned the meaning of "mine and yours." You might try leaving a box of things that you don't mind giving up that your brother can play with safely. From time to time, put some new things in the box. Maybe your brother will find the contents of the box so interesting that he'll forget all about those items you don't ever want him to touch. Remember, your brother will get older and, in time, he'll gain an appreciation for the ideas of ownership and privacy. But for now, keep particularly special items out of his reach.