What are the Qualifications of Gigantisism?

My father is 6'4, my mother is 5'10, and i'm 6'3 at the age of 14. On top of my height is my shoe size. I currently require a size 18 shoe, and i'm afraid i'm not finished growing yet. It's not a growth spurt randomly at the onset of puberty, though. I've always been significantly bigger (height and mass) than the other kids.