here are the rules all of which have to be met to be able to claim him as a dependent
1) he's unmarried
2) he's a citizen of the US, Canada, or Mexico
3) he meets the test requiring him to live with you or be related. since he's your brother. This rule is met
4) his gross TAXABLE income must be less than $4700.
5) you provide over 50% of his support.
see this IRS worksheet to compute your support
https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
