The king during the events of Rage of Bahamut: Genesis was Charioce XIII (he's introduced as such when Favaro and friends are brought before him in episode 6). The destruction wrought by Bahamut in episode 12 ends up killing him.
The king at the start of Rage of Bahamut: Virgin Soul, just ten years later, is Charioce XVII (introduced as such when he returns to the capital in episode 1).
That leaves a gap of three Charioces unaccounted for. What happened to Charioces XIV through XVI? Did Anati really have four different kings in the mere ten years following Charioce XIII's death?