the tax law is not whether they WERE claimed but whether they COULD be claimed. so if you COULD claim them they must indicate this on their return despite the fact that you don't claim them.
if a dependency deduction for an individual is allowed or allowable to another taxpayer (you), the dependent can't claim the AOTC, and any QT&R expenses paid by the dependent are treated by the person who is allowed the deduction IRC Sec 25A(g)(3)
although the dependency exemption is suspended from 2018 to 2025 IRC SEC 151(d)(5)(B) provides that the suspension isn't taken into a/c in determining whether a deduction for personal exemptions is "allowed" or "allowable". so a student for whom a taxpayer (you) could, but for the suspension, claim a dependency exemption, can't claim the AOTC
in short, whether you claim him or not, he can't take the credit because he qualifies as your dependent.
