Bowser has only one son?

[Davy Jones]

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.