Count of Guiche
He was quite a prominent figure in Court and bisexual, so perhaps a lover of Philippe as well as being one of the rumoured fathers of Henrietta's baby (the other two being Philippe and Louis). Is he in this? I'm surprised they'd leave such an obviously dramatic and colourful character out considering his sexual liaisons with just about everybody in Court aside from the King himself, but I can't align him to anyone on the show.
Weirdly if you type Guiche de Gramont into google, you get a lot of results about a handsome blond manga character that is loosely based on the playboy count.
It's too cerebral! We're trying to make a movie here, not a film!