I discovered my tendency towards kink at a very early age, stumbling upon my father's pornography. I do remember talking about about the images with another girl in my class, which must have been like 2nd or 3rd grade, since I distinctly remember it being in Catholic School and those were the only years I went. It didn't take. In truth, she was probably my first crush too. I don't remember anything about her other than those discussions and that she had red hair.
Growing up, there was no shortage of porn to be found. He always rented videos or bought magazines, and did a terrible job hiding them. In any case, I was always drawn to the images, or the Penthouse letters, or the scenes, that had some relation to BDSM. The restraints, the scenes with spanking, etc.
It didn't necessarily cultivate into a full-on realization that I was more into that than vanilla until college, when I could explore my fantasies a little more via the internet. Its not that I don't like a good deal of straight porn, just when its rough. I just like the stuff a little more on the fringes.