When I was 5, my mom & dad gave me my first kit, a Model T. I think it was a Lindberg kit, but I don't remember exactly. I do remember metal axles, and using Duco Household Cement to assemble it.
From there, Mom and Dad gave me simple kits. Since I was nuts about dinosaurs, they gave me all of the Pyro/Life-Like dinosaur kits. As I got older, I became interested in history, especially World War II, and so, I got ships, like Revell's 1/720 Arizona and Pennsylvania (same sprues), and their larger ships, and airplanes-again, Revell, and Monogram.
As I got older and started getting an allowance, and then pay from various jobs, I started buying myself the kits. Though, I got the big Monogram kits for Christmas and my birthday. And I had an uncle who would take my to Kiddie City when we visited, and he would let me pick out a model and buy it for me.
All the while, I would read about the subjects, and watch movies and TV shows. That fueled my interest. And I got interested in science fiction, so I added those kits, too.
By the time I was in high school, I had discovered miniature figures, mostly Airfix, and from periods from Ancient Greece and Rome, to World War II.
But it was my parents and family who helped foster the interest, till I could keep it going on my own.