There is no such thing as a "former dependent" on a tax return. You either claim the dependent or you do not claim them. If he can be claimed then on his own return he has to say he can be claimed as a dependent. If he does NOT meet the criteria for you to claim him, then you do not enter anything at all about him on your own tax return.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
