And that is just one of the main characters...

katara and zuko were probably the first ship i ever shipped

And is it just me or wasn't katara a couple of years older than aang? I think he was around ten and she was around 13...

I always got the impression that he was twelve and Katara and Sakka were like 14 or something.

Your impression was correct, Tits.
According to the Avatar Wiki, Aang was 112 (or 12 biologically) and Katara was 14.

See? Super freaky, can you imagine a 14 year old dating a 12 year old? I mean 14 yos are teenagers and 12 yos are kids!