I was about 6 or 7 when I was was drawing a bit but officially started to draw when I was 10 or 11 years old when I did.

I believe I was about 4 to 6 years old. First thing I remember drawing was a picture book that was essentially Goldilocks and the Three Bears fanfiction.

Probably 9 or 10 when I started to really get into drawing. Drew bad anime versions of Regular Show characters and Vocaloid fanart.

Kindergarten, drew a lot whenever we were just sitting around, inbetween playing.

I recall the main reason I kept drawing was all the positive reinforcement I got from the adults and some of the kids around me.

I know I was drawing before I started school, so that's at least 5 years old, possibly as early as 3 if I'm remembering the doodle Mom salvaged correctly. My style is entirely self-taught and developed in several discrete stages—a major shift occurred in my teens when I brute-forced my way into "realistic" detail (read: heads have actual shape and aren't just embellished circles). When I started drawing for DYOS I was at 'Stage 4', rough but passable, with a few freak incidents of borderline competence, but within two years had honed it to the point I was no longer immediately cringing at the output. :^) I consider my current calibre 'Stage 5': relatively consistent quality where accurate proportions are the norm rather than the exception, and that can even manifest in conscious skill.

Me when 3-4 years?

I started drawing just random doodles at a young age but really only started taking it more seriously when I was around 19/20. 

Probably around three or four. At eight, I was copying pictures and using my Power Ranger toys as models. I started gathering 'how to draw manga' books in high school.