Well, I put Bowser and Mario at about the same age, maybe Bowser a BIT older. In my opinion, both are in their early thirties. Of course, this doesn't matter much, concidering that they are cartoons and will live forever! ;)
As for the Koopa Kids...A little harder for me to guess, cause I kinda like to imagine them all getting dropped off by the storks as one big package of punishment for Bowser. But, just by looking at them and judging from their appearence, I'd say
Roy 16; Ludwig 15, Larry 14, Wendy 13, Morton 12, and the twins 11.
I put them all in the teen/preteen ages cause they seem to be more reckless and destructive teens than puny little kids. Teens would pose more of a threat, anyway. Heh heh.
I'd never really thought of that before, really. Good question! Next!
--Roy Koopa
--Oldest and coolest of the Seven Koopa Kids!
"What? You don''t think I''m the oldest? Come here and say that!!"