King George VII
Possibly George VIII
There’s been some speculation that when/if he ascends the throne, Charles will take the name George VII. Both in honor of his Grandfather (who was actually Albert/Bertie and took the name George VI in honor of George V) and because there’s a heck of a lot of bad karma associated wtb English kings named Charles.
Prince Philip, the village idiot grandfather, has expressed a desire to be known as King George when / if he ascends to the throne. [Monarchs, like the Pope, can make those kind of name changes.] If so, I assume the Royal Heir would be King George VIII.