In Super Mario Bros. Bowser appears as the final boss (King Koopa)
In Super Mario Bros. 3 Bowser has 7 children: Larry Koopa, Morton Koopa Jr., Wendy O. Koopa, Iggy Koopa, Roy Koopa, Lemmy Koopa and Ludwig Von Koopa. Yet there is no sign of a post pubescent female.
In Super Mario World Bowser appears with his 7 kids faced in a different difficulty order (some of them have been practicing and some of them have been lazy, I'm talking to you Iggy).
In Super Mario 64 Bowser has no children, and the Koopa family name seems to have vanished.
In Super Mario Sunshine Bowser Jr. appears for the first time as a small confused child informed that Princess Peach is his mother.
In Super Mario Galaxy Bowser has 1 (one) child, Bowser Jr.

The facts, ladies and gentlemen, are perfectly clear; the theories however, are abundant and foggy. Where exactly did the original seven Koopa children come from? and for that matter, where did they go? Who would be willing to have sex with Bowser no less than 8 times? Why is Wendy the only female bowser? (although I have my suspicions about Roy). Why is Bowser Jr. so goldanged cute if he's supposed to be evil? These questions, and more will be repeated, and possibly answered, the next time my brain shuts down after playing Super Mario Galaxy for 4 hours straight.