The capital of the Utra country was placed near the borders of the nation.
As the city that held the highest power in the country, it was the best line of defense in case of an attack from enemy nations.
The Royal dynasty wasn't the only noble family that occupied it, there were many small and medium-size families that were annexed in the borders of the capital.
A single family could not have the power to rule over a nation for two thousand years without accidents occurring, it needed to have a man-power that vastly surpassed any one of the other large-size noble families.
The Elbas family solved that issue by linking many smaller noble families to their rule, giving important positions to them and connecting their heirs with political marriages.
Like that, the number of their descendants was largely increased and they could rely on them to take care of important structures of the Royal city.
Thaddeus and Lisa were precisely two of those descendants with mixed blood.