Complex sentence: Traditionally there had been two Druze socio-political branches living in the Jabal Amel region: the Yemeni were headed by the Hamdan and Al-Atrash families and the Qaysi by the Jumblatt and Arslan families.
Split into simpler sentences: Traditionally there had been two branches of Druze living in the Jabal Amel region. The Yemeni Druze were headed by the Hamdan and Al-Atrash families and the Kaysi Druze were headed by the Jumblatt and Arslan families.