King James Surname was Stuart

https://en.wikipedia.org/wiki/James_VI_and_I



And Queen Victoria's surname would have been Frederick.

https://en.wikipedia.org/wiki/Queen_Victoria
https://en.wikipedia.org/wiki/Prince_Edward,_Duke_of_Kent_and_Strathearn
https://en.wikipedia.org/wiki/George_III_of_the_United_Kingdom

And current Prince Charles real surname would be Ludwig.

https://en.wikipedia.org/wiki/Friedrich_Wilhelm,_Duke_of_Schleswig-Holstein-Sonderburg-Gl%C3%BCcksburg

or August?

https://en.wikipedia.org/wiki/Friedrich_Karl_Ludwig,_Duke_of_Schleswig-Holstein-Sonderburg-Beck

or  Frederick

https://en.wikipedia.org/wiki/Peter_August,_Duke_of_Schleswig-Holstein-Sonderburg-Beck