If you've read book 1 - Children of the Sun and Moon - you understand that the rulers of the Central Lands (Free-Realm) are the Traven's. This wasn't always so. In fact, it was this family that joined the two ruling classes together.
Once upon a time...
There were 2 powerful families. There weren't many settled in the area known as the Central Lands so these two families prospered. When the area began to see more people, it was decided that a ruler should exist to help settle all matters in regards to the area. Since there were only 2 families to have influence over others, a council of peers was created to decide who should rule, and when.
At first things were petty. Each side attempting to curry favour from the council. Eventually things mellowed out, and each side would take the council's choice without argument. This, interestingly enough, coincided with the wizard fortress turning into a school, and bringing more people into the area. (The school thing is due to Gillock, and will be explained one day)
The two ruling families were Traven, and Klayhern. Usually rule kept with one side until no heir was born, or something happened to the children before they were of age to take the throne. Also, only current rulers children can take the throne. If they have none, and the family title changes to Duke/Duchess, a sibling to the throne, or even a distant cousin, now becomes thrust into the realm of noble intrigue.
So where am I going with this?
I needed to create royal lineage for the trilogy I am working on now. It will also carry over to another trilogy at a later date. It's interesting because there is a Duke/Duchess and King/Queen. When one side can no longer rule, someone from their family line becomes the next Duke/Duchess. Since only children from the current rulers can take the throne this creates some fun times in creating the lineage.
So far I am having a lot of fun, but I have only just started mapping it. I'm certain my brain is going to go into overdrive, or melt. Either way, at least part of this will be written.