The above article, while very informative, didn't really get into the "birth order" theory. I've read that in the case of bicolor cats, the warmer the spot in the womb a particular kitten occupies, the more white it will have. I don't know if it's true or not, as it sounds like the idea came from the Siamese "points", but it certainly pretty much describes the litter JC was born in. His mother was a white cat with black ears and tail, and his (suspected) father a huge, long-haired gray tabby. The kittens, in order of birth, were:
1. a gray tabby female, 2. a bicolor male, approximately 75% - 80% black, with a white chest and front legs, 3. JC, roughly 65% black, 4. a bicolor male, 75% white, 25% gray, and 5. a bicolor male, 50% black, 50% white (oddly enough, half his face is white, the other half black). JC was the largest, and the gray and white kitten was the smallest. His gray is on his face and back.
And here's an oddity about the Siamese. Former neighbors in Philadelphia moved to Miami Beach. One of their cats, a seal-point Siamese, "faded" after living down there for a while. His points went from brown to almost beige.