My mom wasn't fat but heavy set and busty. As a kid I liked playing with her hair and eventually enjoyed when she tickled me, in my thrashing around I would grope at her big 38C's dangling in front of me. She was keen to what I was doing and soon stopped entertaining my perverse activity...

 

A few years later I was in fourth grade. Puberty strikes at wild times, and in my case an admirer was struck with an irresistible attraction to me. I'm Hispanic and was tall for my age at the time. I don't know how it started but Myka, a fat blonde girl with blue eyes and no particular bustiness, started chasing me during recess at school. I was already familiar with racial tension due to the area I grew up in, so this was kind of an amusing and curious sensation. But even then I fantasized about Myka, standing on my desk at home and me eating out her presumably overgrown blonde bush, an exotic contrast to my own dark skin and black hair.

 

So I think this might have planted the initial seed for my taste in larger women - being birthed by one, then being pursued by another. It certainly doesn't hurt that they typically have much bustier frames and more plump bottoms...