Complex sentence: During this process, Orgetorix had also succeeded in making a personal alliance with the Sequanii chieftain Casticus and the Aedui chieftain Dumnorix through marital arrangements and host exchange of family members.
Split into simpler sentences: During this process, Orgetorix had also succeeded in making a personal alliance with the Sequanii chieftain Casticus and Dumnorix, chieftain of the Aedui. He accomplished this by way of marital arrangements and host exchange of family members.