Bowser has only one son?

[NICKtendo DS]

My guess is that it's NOA material only and that Europeans, etc. adopted it. The Japanese translation for the Koopalings is "Bowser Kids", not "Bowser's Kids", but it's still hard to believe.

Ah yeah, and I've also wondered about Morton Koopa Jr.~

For the mother: I guess it's just like in Dragonball, Frieza has no mother and just King Cold who made him. Same goes for Piccolo, his father spitted an egg off his mouth and even Cell doesn't need a female counterpart to make kids. Furthermore, Yoshi in SMW can lay eggs without problems, so I don't see any need for a mother in this franchise.

Wendy says hi.

While they're not Bowser's children (apparently), I always thought Bowser was their uncle. This could be true, but we'll never know until it is proven in-game. You can't rely on Miyamoto about this, because he might aswell be lying because he has to keep it a secret. Perhaps it's even a plot point somewhere in NSMBU, though that may be a little far fetched.