Head of Family
Unlike many other cultures in Essos, the Valyrian family unit is male preference primogeniture, which is a form of primogeniture in which sex is irrelevant for inheritance; the oldest surviving child without regard to sex rules the family and is known the Head of Family (HoF).
The only exception to this rule is when upon the death of a HoF, the next in line of a dragonlord family is not bonded with a dragon.
Their Scope
Heads of Family hold special legal powers and privileges that give them absolute jurisdiction over all the members of their family.The laws of the Freehold do their best to keep Dragonlords from tearing each other and Valyria apart. The entire peninsula, and the Freehold at large, exists in its current state by a complex series of checks and balances.
Family is everything. The beginning and the end, they are empires in their own right, conquering and controlling whatever is not already conquered and controlled. Or, making moves to take over what has been conquered already either covertly, aggressively or by political maneuverings.
As for the power dynamic within the family, they are the patriarch/matriarch, and the siblings, children, grandchildren are kept in line by tradition, culture, pride and a healthy amount of fear.
Inner-family wars are no where near as prominent as inter-family wars. Even when rifts form within, they keep the overt drama to a bare minimum lest another family get wind of the turmoil and look to incense things further and reap the reward of their distraction and division.
A HoF has the power to outcast a family member. Which for a Dragonlord would mean being unbound from their dragon forcefully and sent into exile. The threat of this usually keeps dragonriders in check.
To go against ones HoF and be caught, would be disasterous for the member.
This of course doesn't include trying to get rid of the HoF secretly and getting away with it.
Should they attack or usurp publicly it would show disunity and weakness which could spell the very end of that family.
