Well we've got Lucina and female Corrin representing Fire Emblem Princesses.
Full list of Smash Royalty is as follows
Undesputed
Peach: Princess of the Mushroom Principality (Not a Kingdom)
Bowser: King of Koopas
Daisy: Princess of the Kingdoms of Srassaland (technically should be Empress Daisy)
Zelda: (Several) Princess(es) of Hyrule
Ganondorf: King of Thieves, King of Evil, King of Conquered Hyrule
Rosalina: Not a princess per se but shares the aesthetics
Marth: Prince -> Hero King
Chrom: Prince -> Exalt
Lucina: Chrom's Daughter
Corrin: Prince/Princess of about three different lines. (It's complicated)
King K. Rool: Leader of the Kremlings, no matter what title he attaches to his name.
Debatable
King Dedede: Make that "King" Dedede
Robin: Potentially can marry into royalty
Very Debatable
Sonic: The True King Arthur
Donkey Kong: Sometimes referred to as the King of the Jungle but I don't think that's a recognised kingdom.