If he meets the requirements below you can claim him.
The 4 tests that will qualify a relative as a dependent are:
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Qualifying Child: They are not the “qualifying child” of another taxpayer or your “qualifying child”.
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Gross Income: The dependent being claimed earns less than $4,050 in 2017.
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Total Support: You provide more than half of the total support for the year.
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Member of Household or Relationship: The person (a friend, girlfriend, non-blood relative) must live with you all year as a member of your household.
https://blog.turbotax.intuit.com/tax-deductions-and-credits-2/family/who-can-i-claim-as-a-dependent-...