I can't imagine anyone starting earlier than my age, honestly, because it requires a lot of reading, to figure out what to do next. <.<
I started playing Red when I was 6 years old, same year it came out. I became hooked immediately and had all the gameboy accessories, and watched the anime every day after school and I had a pokemon lunchbox and pokemon school supplies... I had pokemon pencils, pokemon erasers, there was a pencil sharpener where you stuck the pencil into Bulbasaur's bulb. I had pokemon folders ( ゚ヮ゚) they were my favorite. I would practice drawing like, Jessie and James and Meowth and I also drew Charizard a lot.
hehe I also remember a pokemon ice cream cake for my birthday!