Spoilers for my books ahead, of course.
When I wrote my debut novel, Remnant, I wrote the main characters to all be based on people I knew. The interesting thing is, I originally conceived the story as a teenager and the main characters in Remnant are based on people in my life when I was 16. That’s how it started, anyway. It didn’t always stay that way…
Theia, the main character of the whole series, is not based on anyone I know or knew. Her character is based on a concept. She’s based on my desire to be a father and what I want my future child to be like: strong, intelligent, principled, altruistic.
As anyone who has read Remnant and/or its sequels already knows, Theia’s father is Ethan, and given what I wrote in the previous paragraph, obviously Ethan is based on myself. To write that character, I took into account all of the things I know about myself and combined them with how people generally perceive me, and then amplified all of it. I made his dark side extremely dark, and his good side too good. What does ‘too good’ mean? Well, if you read Remnant, you’ll notice that Ethan’s entire purpose in life revolves around his daughter. He’ll do literally anything he has to in order to protect her, to the degree he has no other purpose in life at all. That’s unhealthy, I think. So, like I said, I amplified all of my own traits/qualities to near-maximum levels.
Now, there’s the rest of the main characters in Remnant. The character of James is based on my own best friend, and for James I hardly changed any of his personality from his real-life counterpart. With James’ wife, I originally based her on my best friend’s girlfriend at the time, but that ended up needing to change completely to fit the story; so, in the end, James’ wife Candace was not based on anyone.
Mercy is not based on anyone. Seth was also originally based on someone I knew when I was 16, but the characteristics Seth needed to have didn’t entirely match his original real-life counterpart, so, ultimately, Seth isn’t based on anyone as well.
Basically, that just leaves myself. And even then, I have some stark differences with Ethan. As a few obvious examples, I’ve never been involved with the mob, I’ve never killed anyone, and I don’t have a twin sister.
Speaking of Ethan’s twin sister, Lilith, who is the main antagonist in Resurrection, I did base her on some real-life people: my first girlfriend, and my actual (older) sister. Both had a manipulative, unapologetic nature, and both are people I once loved who I no longer love because of who they are as people. Just like Ethan does in Resurrection. Of course, I amplified those bad traits for the character of Lilith (also like with Ethan). Some more differences between Lilith and her real-life counterparts is her appearance (neither my first girlfriend or sister have red hair or tended to dress in black and red) and her past. Desite Lilith’s bad traits, she is very loyal to her brother Ethan; something neither of the people she’s based on were to me.
When time came to start writing Relics, the third volume in the series (which I’m 10% finished with), I decided to truly base characters on people I know. I asked one of my longtime friends if she’d be okay if I based a new character on her, with the same name and personality; she just laughed and said sure. I also asked my best friend if I could base a new character on him, because I don’t like that the previous one died.
As a general idea, I think it’s good for authors to base characters on real people, especially if they personally know/knew those people. It helps tremendously in making those characters feel real. Writing characters requires you to get inside of their head, so that you know what they’ll do next. If you love the real-life people these characters are based on,it helps you realize they’re not perfect, and if you hate those people, it helps you realize they’re not completely evil.
It’s part of what makes writing so much fun, and so educational.