“The rumor appears to have entered into the mainstream media recently as a result of another joke made about it on The Late Show with Stephen Colbert.”
Laughable nonsense, the “rumors” were around long before Colbert did his piece.
Here is a New York Post story from last year
and one from the Daily News
https://www.nydailynews.com/2023/12/02/prince-william-affair-rumors-palace-officials/
Right around the time that Sparkles was hitting a brick wall in her efforts to redo the British monarchy.