According to the Hanafi Madhab, joining 2 Salaat in one time is not permissible. The ?joining? in the Hadith is taken to be performing one Salaat at the end of its time and next Salaat at the very beginning of its time.
In the abovementioned situation, the brother should not join them. If the Salaat they are joining (bringing forward) is Asr or Esha, then he could join them with the niyyah of performing Nafl Salaat.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai