There is no more personal exemption. Everyone gets the same Standard Deduction now. Although a dependent Deduction might be less. Even if you don't claim him he might still qualify as your dependent.
Does he qualify as your dependent? Who can you claim
https://ttlc.intuit.com/community/credits-and-deductions/help/who-can-i-claim-as-my-dependent/01/267...
Does he need to file a return? Be sure on their return they check the box that says they can be claimed on someone else’s return. If their only income is W2 and under 12,400 they do not have to file a return except to get back any withholding taken out.
Filing requirements for a dependent
https://ttlc.intuit.com/community/children-dependents/help/do-i-need-to-file-my-own-taxes-if-i-m-a-d...
