Patriot, what a good older brother you are! I'm going to take my best shot at giving you some suggestions...
I suppose you have already had a heart to heart talk to your brother...but if you haven't that would be my first idea. tell him how concerned you are.
Try to spend time with him. If he sees what your life is like and that you have plans and how happy you are to be working toward some goals, maybe this will inspire him. Sometimes just one good influence can make a big difference in a kid's life. Maybe he looks up to you, i always looked up to my older brother. (Mine was the first one to get me high, tho).
A good resource for almost anything is the United Way-they have a website and they are nation-wide. They also have a number, it should be listed in the phone book. tell them your situation and they can connect you with resources in your area.
If there is a center for runaway youth in your area, drop by and ask them for advice.
I know your brother is not a runaway, but these places have experience dealing with youth and their issues, and they night give you some good ideas.
You said that you are going to school-does your school have Human Services or Social Work courses? If they do, talk to one of the instructors of these classes, they might have some good ideas.
I hope this helps.
Hugs....