Neither options apply to me.The average denizen of PF has an above average interest in math. It's my preconception that people don't well at math unless it's reinforced at home. I could be wrong, though. It could be that some people discover it in school and take off with it despite indifference to it at home.
I've put two options. The first is that you got a good opinion of math at home, that your parents spoke of math as a good, important thing and encouraged you to do well in it.
The second is that your family was indifferent or even hostile to it and you got your interest from exposure at school and good experiences in math classes. Math intrigued you despite your family members speaking of it as "boring," "tedious," or "bleh", and the bulk of your encouragement came from your teachers.
Option one probably encompasses option two, but option two does not encompass option one. That's why I've limited it to two. Feel free to explain any third situation that applies to you.
My first kick to go and learn more advanced math was the realization that it can help me understand reality better; I started reading pop books in cosmology and physics, and thus the spark began.
In school you don't get to talk on cosmology or cool stuff in physics and math, and most of the tasks in HS or Primary school is mundane. In home neither of my parents have an education beyond HS nor an interest in physics or math.
Self made man, I guess.