Writing WHO You Know

How do you create characters? This has always been an interesting question for me. When I was little, maybe out of some kind of loneliness -- but more likely just because I was a weird little kid -- I used to write character sketches. I liked to create whole people, noting down everything I could think of about them. I liked to pretend that I knew these people, and thought it was exciting to play God with them, to get to decide every little detail about them (right down to the part where they thought I was the coolest deity ever!) I didn't realize it at the time, but I was basically practicing for building out characters for my later stories, and I still use a lot of what I discovered was useful back then. That said, I still struggle sometimes with realizing my characters -- keeping them rounded and fully dimensional. We're users, as writers. We create characters often because we need them to do something, to move the story forward, to be a certain thing and serve a greater purpose. And when I've built someone and used them in this selfish way, sometimes I drop them like yesterday's fish dinner, forgetting that they must go on to some degree to be believable.

So here's the question -- or the thought at least. And be warned, it isn't exceptionally original except that I've only just thought of it myself in the context of my own work:  Do you write people who you know in real life?

Here's why I'm really asking. I'm in a creative tornado right now, where I am filled with ideas and keep starting lots of things, some of which I'll continue to work on, and some of which are useful only in their own moment. One of these things is a middle-grade story that would be interesting to my own kids. Starring? Two boys who mysteriously share quite a few character and personality traits with two other little boys who I know quite well. Coincidentally the two boys in the story are brothers. Okay, it isn't a coincidence at all. It's an experiment to see if the characters I base unabashedly on real people are more lifelike and multifaceted than those who I create from thin air. These boys are older than my own, because my two year old still doesn't express himself too clearly and having a lot of dialogue where the younger brother says things like, "A hafta shaff go nuff POO!" would probably not keep readers engaged.

Have you tried this before? How did it work for you?