If he qualifies as a dependent, he cannot claim his own personal exemption.
See the following from IRS
Publication 501:
Dependent not allowed a personal exemption. If you can claim an exemption for your dependent, the dependent can't claim his or her own personal exemption on his or her own tax return. This is true even if you don't claim the dependent's exemption on your return. It is also true if the dependent's exemption on your return is reduced or eliminated under the phaseout rule described under
Phaseout of Exemptions
, later.
