Dana Shilling
The series doesn't give us a lot of information about many aspects of daily life, including civil law. If we assume a property system something like Elizabethan England, though--a system dominated by elder sons, with an obsessive concern about "legitimacy"--it could explain a lot.
Keeping in mind what Ellynne said earlier--that American's don't write giants well because they don't occur in their native mythology--it's interesting that Americans and English often assume that the most common method of inheritance is primogeniture.