OK theory time!
What I said about Ash looking similar with the prince and their mansion previously resided by the queen dowanger - there is a possibility that Mil's timeline happens after Cinderella got the prince.
My hunch is the queen is Cinderella and Walton is the fairy godfather.
It was mentioned that she believes in destiny which could mean what happened at the ball in the Cinderella story.
Walton's confusion of the "eldest" Barnes could mean that he is an older being.
Also, consider the ton of privilege as he strolls around the palace despite having a mere title of a Baron and a traveler at his belt could mean as a cover to have him around Cinderella.