You cannot claim him unless he is a full time college student, or he earned less than 4,050. See the following rules:
He is a full time college student:
To be a student, they must be, during some part of each of any 5 calendar months of the year:
A full-time student at a school that has a regular teaching staff, course of study, and a regularly enrolled student body at the school, or
A student taking a full-time, on-farm training course given by a school described in (1), or by a state, county, or local government agency.
The 5 calendar months don't have to be consecutive.
He did not file a joint return.
He did not provide more than half of his support.
If he is not a college student, the following must apply:
He earned less than 4,050 dollars
You provided more than half of his support.