Complex sentence: Finally Boris recruited his younger brother Arie (then only 14 years old) has joined as the lead guitarist, Itamar Cohen on Drums and Maor Bitton on the Bass.
Split into simpler sentences: Finally Boris recruited his younger brother Arie (then only 14 years old). He has joined as the lead guitarist, while Itamar Cohen joined on Drums and Maor Bitton on the Bass.