As long as he meets all the qualifications.  Take a close look at last three.

You can claim a child, relative, friend, or fiance (etc.) as a dependent on your 2018 taxes as long as they meet the following requirements:

Qualifying child

• They are related to you.
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They are under the age of 19 (or 24 for full-time students).
  • No age limit for permanently and totally disabled children.
• They live with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year