Hi XXXXXXX
Thank you for using justanswer. You may claim your brother as your dependent under the Qualifying Child rules if he is under age 19, (or age 24 if he's a full time student), he lived with you for more than 6 months, and he doesn't provide more than 50% of his own support, and he is not the qualifying child of anyone else, such as a parent. Please see below:
Publication 501 (2007), Exemptions, Standard Deduction, and Filing Information
I hope this helps.
Master Tax Preparer
Enrolled Agent with 20 Years Experience specializing Individual and Small Businesses