I'm sure the retcon for the Koopalings roots, at lest in part, in how them and Bowser Jr. being Bowser's biologcial children just wouldn't be family-friendly enough according to their owners. When you take Bowser having 8 really different looking children combined with him obviously having a romantic interest in Peach, it's not hard to get the impression of harems and concubines (since Bowser has never been shown with a wife).