Concerning Bowser Jr. and the Koopalings...

The Great Gonzales

The Glitz Pit Champ
Could someone explain this to me: Why is Bowser Jr. separate from the Koopalings and classified as Bowser's 8th child. In my opinion, it is more likely that Bowser Jr. is Baby Ludwig. Think about it: Why would Bowser suddenly stop using his seven older, more skilled and mature children in favor of one younger, les mature child? That doesn't make sense. Given the fact that the original 7 are never mentioned when Bowser Jr. is present, it seems to me that Bowser Jr. is the first of the Koopalings.

Now, I know someone will say, "Well, in Super Mario Sunshine there's a quick scene of Mario fighting Iggy from Super Mario Bros. 3", so I'll respond to that here: The fact is, that scene is just a quick little easter egg and does not necessarily mean anything in the grand scheme of Mario. Link made a cameo in Super Mario RPG, but does that mean Link and Mario live in the same world? I don't think so.
If FLUDD was scanning Mario's mind, though, it would have shown the battle with Iggy from a first-person perspective. Mario sees through his eyes, not the camera, after all.