You will want to make sure that the person you are claiming qualifies as a dependent.
Please see this article for information on who can be claimed as a dependent,
then review the dependent information in your return to see if you have
answered the questions about your dependent correctly: http://blog.turbotax.intuit.com/tax-deductions-and-credits-2/family/who-can-i-claim-as-a-dependent-7...