Although my family was fairly middle class, my siblings (as well as me) were avid readers. My older brother liked to read about the Napoleonic wars, Roman civilization and who knows what else. He later became a politician in Alberta. He also read science fiction and when he moved out I discovered various SF novels lying around, such as Frank Herbert’s Green Brain. There were other Herbert and Heinlein books and I devoured what I could.
But prior to those pure SF authors, I had fed on fairy tales and Norse myths at a younger age. I remember reading The Water Babies, and one book that illusrated the myths in vivid illustrations. I don’t have that book but I found one by the same author/artists (?–I will fill in the name later) a few years ago in the US and bought it. It was on Greek myths so I added it to my collection: another recovery of the magic from my childhood.
I also read many Nancy Drew mysteries, left by my older sister. My mother bought me new ones and I spent enough nights with the flashlight under the cover reading. There were a few Hardy Boys lying about and I read all of those too, plus some historical and/or romantic fiction that my mother had read.
The true transitional time from fairy tales and Aesop’s Fables to SF and fantasy was when I was about twelve. I had read some Edgar Allan Poe and then went on to Ray Bradbury, and from there straight on to SF & fantasy. I remember having to make a newspaper in grade 7 with other classmates. Our group’s had a decidedly speculative element and I wrote articles or drew pictures of aliens.
Today, my siblings still read voraciously. My older brother still reads about politics and SF, when he has time. My younger brother reads more fantasy. My sister reads true crime and mystery novels. I read SF, fantasy, mystery, historical and literary, from time to time. My mother reads mostly on politics when she reads. She falls asleep more now. I’m not sure what else they read but maybe I’ll poll them.
I guess my fascination with the worlds of what-if began at an early age.