I prefer to split the difference on the “are the Koopalings Bowser’s kids or not?” question by supposing that they’re the children of various noble families that Bowser is fostering at his court, because a. that’s a thing that real-life royalty often did, both to provide the kids with networking opportunities and to keep them handy as hostages against their families’ continued good behaviour, and b. it requires us to posit the existence of a Koopa peerage, which is entertainingly deranged, especially when you start to consider what sorts of noble families would produce these particular heirs.
i’m gonna assume a Hapsburg scenario of large, closely related noble families practicing endogamy, possibly as a result of a dwindling base of unrelated nobility—which would also explain Bowser being the princess-snatching type beyond just land grabs that could be achieved with military force.
How does the fact that Bowser himself lacks biological parents, was raised by the court wizard, and was likely delivered by a stork fit into this?
It’s a Romulus/Remus-esque origin. Bowser is the legendary culture hero of all Koopas, born ex nihilo (per ciconia?) and molded as Arthur into a figure who could unify his otherwise unionless peoples.