Sebastian is afflicted with a hereditary genetic condition known as Bithil Syndrome. It gives him yellow eyes, incredible hearing and eyesight, quick reflexes, and (although he'd have no way of knowing it without an x-ray) a funky lower vertebra. Although I have been accused (rather nastily, I might add) of making this up, I didn't. I swear, I didn't. The problem is, there are literally thousands of weird syndromes, and most of them are so rare that if you look them up on Google, you won't find them. But just because something doesn't turn up in Google doesn't mean it doesn't exist.
So how did I hear about it? Well, it all began some eleven years ago when my older daughter took a freshman biology course at LSU. For extra credit the students could volunteer to have their DNA tested, and so she volunteered. Because we were very interested in genealogy at the time, she called me up rather excited to tell me she had this weird thing they called "Bithil Syndrome," and they had asked to run more tests on her. (To complicate matters, she may have misspelled it; it could actually be Bithel.) Eventually, the geneticist told her she had the purest expression of the syndrome they'd yet found in the western hemisphere. Now, I've always known my daughter had incredible, unnatural hearing; when she was a little girl, you could whisper something in the living room, and she'd open her bedroom door at the other end of the house and shout, "I heard that!"(Yes, it was a pain.) She could read highway signs waaaay down the Interstate. The only aspect of it she doesn't have to any great extent is the quick reflexes; hers are only slightly above normal. And she doesn't have yellow eyes because the color is recessive to brown and, like me, my daughter has brown eyes. But my father had yellow eyes. He was also an incredible marksman and, when we were kids, he spent a great deal of his time yelling at us not to make so damned much noise. So I know exactly where it came from.
Since I was in the middle of developing my idea for the Sebastian series at the time, it seemed like a cool thing to give Sebastian a real genetic condition that made him just a little bit different. It also provides an unusual, identifiable thread for him to follow in his quest to untangle the questions about his paternity (something that comes up again in a significant way in Book #11, which I'm writing now). If I'd been clever, I'd have contacted the geneticist involved and asked for more information, but I didn't, and at this point my daughter can't even remember his name. Because she's now a medical doctor herself, she keeps promising she's going to look it up for me. But she's still a resident and I quit holding my breath long ago.
So, do I have the syndrome? Yes and no. I have that damned funky vertebra in my lower back. But my eyesight was seriously damaged when I was in oxygen for a week after birth. I do still see very well at night (I only recently realized that most people don't see what I see), but the down side to that is that bright light kills you and family members who don't have the syndrome constantly complain that you keep your house dark. Ironically, from my mother I inherited another genetic defect that causes hearing impairment. In me, it averaged things out so that my hearing is only slightly above normal (enough that I am still driven crazy by electric hums that most people don't hear and I wear earplugs in the cinema). But my younger daughter, who inherited the one genetic sequence and not the other, is actually hearing impaired. (Yeah, she's cranky about it.)
So there you have it. This is why I generally avoid talking about it--because it's a sort of personal thing, and the truth is that when I started the series all those years ago I didn't realize just how rare it is, or that the series would go on so long, or that this aspect of it would generate so much interest.