Kyan is a rare Irish surname. However, according to Kyan
Douglas, who popularized the name in the USA, that wasn't the origin of his name.
He claims the name just came to him one day while he was meditating. His original first name was
Hugh.
Kian is normally pronounced to rhyme with
Ian, so isn't the same name as Kyan.
Kian is considered a respelling of
Cian, while Kyan is a modern surname form of
Cathan.