I've never heard of male turtles becoming so aggressive towards their mates to the point of tipping them over. In some species of tortoise, competing males try to tip each other over when fighting over a female. This is not a general occurance in the chelonian world. Oh, by the way, most species of turtles and tortoises are able to right themselves if they are tipped.
Anyway, to stear this topic back to where it should be:
Winx: You are right, my theory does make some sense, and it is logically sound, but I don't like it much either. It doesn't seem right. Here is a more traditional theory:
The Koopa kids are the produce of natural reproduction. Koopas, being basically anthropomorphized turtles, share many traits with real-life turtles. They are social to an extent but they don't form close-knit ties with their mates. King Bowser, wanting offspring (or perhaps just obeying a more primal urge), mated with a female koopa. Who? Well, it doesn't really matter much. Could be some random Koopa, perhaps one of high rank. After she laid her eggs, her role as mother ended. I don't think Bowser had her killed off, I just think she really didn't have much to do with the koopalings to begin with. Now, the Koopalings where born just a few years before SMB3, I think. How is it possible that they where so capable so soon after their birth? Simple. They are turtles, remember? Well, meer hours after being born, baby turtles are almost as capable as they would be as adults. They don't have a prolonged "baby" phase during which they are helpless and completely dependant upon their parents. Or, on the other hand, the Koopa kids could be much older than that and we (from Mario's point of view) just never saw them until we had to fight them. As for their small size compared to Bowser, if their mother is a koopa and you buy into the dragon/koopa thing, the Koopalings only have 1/4 dragon blood, whereas Bowser has 1/2.
What do you think? More specifically, what do you think about the whole Bowser's father being a dragon theory? My only sources of evidence for that are the Mario comic and well, that Bowser looks like a dragon and can breathe fire.
-TurtleTek
http://turtletek.botic.com