Here is a word from the Goodfellas at the IRS:
IRS Tax Tip 2013-09
While each individual tax return is unique, there are some tax rules that affect every person who files a federal income tax return. These rules involve dependents and exemptions. The IRS has six important facts about dependents and exemptions that will help you file your 2012 tax return.
You can view or download Publication 501 at IRS.gov or order it by calling 800-TAX-FORM (800-829-3676). You can also use the Interactive Tax Assistant at IRS.gov to find out if a person qualifies as your dependent. The ITA is a helpful tool that can answer many of your tax law questions.