I had goldfish in a bowl when I was 5 or so, but I don't think that counts. My first "real" tank was inspired by a visit to the Shedd Aquarium in Chicago when I was 12. I got it after I returned to Minneapolis and have kept them continiously ever since.
2 1/2 gal
., guppies and probably a couple of tetras and platys. Hard to remember for sure as that was in 1946.
My first "big" tank was a 10 gal
. I got for Christmas later that year. (It was big back then.) My parents were reluctant as they didn't think I'd stick with it.