Mario World?

Something I never understood was the Super Mario World thing.  If the place was named Mario World, wouldn't that mean that Mario was from a long line of Mario Kings and if that were so, then saving the princess would mean that he was saving either his daughter or his sister, but he ends up smooching her at the end.  Can we say incest?  Also, if he was king of this Mario World, then how is he also a plumber?  Last time I checked, plumber wasn't a desirable career, especially for a king. 

And another thing, if Mario is the king, how come his only friends on the planet are a bulimic dinosaur and a guy named Luigi?  Everyone else wants to kill him.  On that note, how come Mario and Luigi never fight together?  Mario screws up and falls to his death in a never ending pit, so Luigi tries to learn from his dead friend's mistakes and makes it past the pit only to get barbecued by a fire-spitting plant with huge teeth.  Maybe you should've gone to the castle the back way huh?  Those stupid Italians deserved to die.