Does the development of your main characters stem from people you know or are they completely formed in your head?
Ooo, this is a good one.
Short answer: Most of the time I have no idea.
Draken from the unpublished EXILE (keep your fingers crossed) was based on a guy from my gym (back when I used to go to the gym...) He's a special ops dude, the sort that parachutes into despots' compounds and slits a few throats. The sort that makes bad problems go away. He completely inspired Draken and I've always had a dream that someday I'd do a reading with him standing behind me, arms crossed, in chainmail. He makes problems go away in Akrasia, too.
The twins appeared to my mind's eye when I was sitting in a pub in England one New Years Eve. See post here about that. In my mind they are wonderfully handsome, but seriously, they are not my type at all. They are tall, 6'5" or so, (big people make me nervous) and blond (my husband is very close to my ideal and he has dark brown hair like I used to have). I knew right off one had long hair and one had short and that was about it when I started writing them. Aidan took on a life of his own from the first word. Kaelin is pretty tough to draw out. I write him ALL THE TIME, for 9 years now, and still he does stuff and I have no idea why. He's just very reserved.
Katriel in LOST PRINCE spawned from a character I was playing with in the Sentinel books called Saxen. They're a lot alike--kick ass, tough as shit to cover vulnerability--but their pasts are very different. Saxen was the most realistic woman I ever made up myself and wrote. I just have a tough time with chicks. Writing erotica has helped that though. Savannah in Quencher in particular, launched my foray into writing women because she had a very interesting dilemma with her bisexuality and getting into a position where she has to choose between a man who wants to marry her and experimenting with her own team.
Oh, and when Jason from Sentinel speaks, it's my hubbin's voice I hear in my head. He's got a goatee like my hubbin, too. I didn't know for years why he has 18 earrings, though. (Hubbins has no earrings) He just did. Now I know why, but no spoilers...