Yes, if all the other rules are met.
A person can still be a Qualifying
relative dependent, if not a Qualifying Child, if he meets the 6 tests for
claiming a dependent:
1. Closely Related OR live
with the taxpayer ALL year
2. His/her gross taxable income for the year must be less than $4,050 (2016-17)
3. The taxpayer must have
provided more than 1/2 his support*
4. He must be a US citizen or resident of the US, Canada
or Mexico
5. He must not file a joint
return with his spouse or be claiming a dependent of his own
6. He must not be the
qualifying child of another taxpayer
If the person is a child, may qualify as a dependent, but because he is not related, he cannot be a
qualifying child for the earned income credit or child tax credit. There's an exception if you are the non custodial parent, you may claim the Child Tax credit, but not the EIC
*If
no one person (or married couple) provides 50% of the support (for example your
siblings are also sending support), then a "multiple support agreement”
(IRS Form 2120) can be used, to allow you to claim the dependent. https://www.irs.gov/pub/irs-pdf/f2120.pdf
