Will Smith was the Fresh Prince, of course, though that’s long forgotten.
There is apparently more than one Gypsy King, if I’m reading the intertoobs correctly. Also several Latin Kings, but I don’t think they sing much.
Another non-rock one: Benny Goodman was called the King of Swing.
We can just start listing genres and think of which act came to be the most definitive.
I’ve heard Yes referred to as the Kings of Progressive Rock, and Lynyrd Skynyrd as the Kings of Southern Rock.
I can’t recall if I’ve ever heard Bob Dylan called the King of Folk, but it’s arguably him. Could be Woody Guthrie tho, depending if we’re controlling for era.
I would nominate Metallica as Kings of Heavy Metal, although Black Sabbath has some claim as the progenitor. Let the debate rage.
The Kings of Alternative Rock? There are so many nominees that it’s hard to think of an obvious one. If U2 counts as alternative rock then I suppose it would be them.
The Kings of Punk? Well, the Sex Pistols is usually the band that comes to mind, but they had such a short career that was more about headline-grabbing mayhem than music. So maybe it should be The Clash, although they stretched the definition of Punk Rock a bit IMO.
Nirvana probably has a slightly better lock on Kings of Grunge, but Pearl Jam still might be a contender.
For Kings of Hair Metal I think it’s a toss-up between Motley Crue, Poison, and Bon Jovi.
Duran Duran are most probably the Kings of the New Romantics.
If Nine Inch Nails are Kings of Industrial, maybe that should be “King of” in this case. Or maybe just say Trent Reznor is King of Industrial and be done with it.
The Kings of Psychedelic Rock? I may have to meditate on that a bit. IIRC the Doors were once called the Kings of Acid Rock, but their legacy is more the Jim Morrison show and a handful of poppy radio numbers. As for the Grateful Dead, despite all the trappings, their music never really struck me as all that psychedelic. But they were the kings of whatever it was they were doing. Kings of Jam Bands, I guess.
I think Weird Al qualifies as King of Pardoy Songs.
Paul Whiteman was the King of Jazz. The fact that a white man named Whiteman was given this title has often been remarked upon.
Roy Rogers was King of the Coyboys (and was a singer), while his wife, Dale Evans (also a songer), was Queen of the West
John Wayne was the Duke.
Al Hirt was called the King of the Trumpet.
Frank Yankovic was The Polka King.
I once heard Judas Priest referred to as the Grandfathers of Heavy Metal.