His age today is irrelevant. What matters his is age on Dec 31 of the tax year. If they still live with you and you provide more than half of their support in 2017, they qualify as your dependent, regardless of how much they earned, provided they were *UNDER* the age of 19 on Dec 31 of the tax year. Different rules apply if they were 19 years old on Dec 31. But you would probably still qualify to claim them under the different set of rules.
