In my first sketches of this current WIP, the protagonist was one of two children born to a single mother. The family began and ended there; these three were each other’s whole world, and nothing mattered but each other.

It’s a very American family structure, which isn’t a bad thing– but it didn’t fit to the world I was building.

I’m not the kind of person who can just make up a thousand characters off the top of my head. I can’t create a family without first fitting it into some kind of structure.

That’s where the family tree comes in. I used FamilyEcho, but you can find plenty of free software online.

In this case, I’m dealing with a royal family, where it’s of the utmost importance to have “an heir and a spare”– meaning that there needs to be a clear line of succession in the event that the current monarch dies. Failure to do so would leave the country open to power struggles and the potential of a civil war, and nobody (nobody we like, anyway) wants that.

That premise gave me some questions to help me flesh out these characters.

• I wanted my protagonist to be an only child. So what would cause a member of a royal family to stop at just one kid?
• Did the protagonist’s grandparents follow the “heir and a spare” rule? Did theirs? Did everybody else in the family? That gave me a rough number for how many family members I’d be dealing with.
• I decided that I didn’t want that many cousins floating around in the background, so I needed to kill a few people off before they had kids of their own. What was a common cause of death among these people? In my case, there was an epidemic that hit the royal family pretty hard in one year.
• How old was each person when they had children? How far apart was each of the pregnancies? What’s the adult life expectancy in this country? Those questions help me narrow down how many people are still alive, their respective ages, and their relationships to each other.

All of that gives me a solid foundation to work with. From there, I can start working on things like names, personalities, and motivations.