D`Artagnan was betrothed to a man several years ago, a man who is nothing but a brute, a man who will treat him dreadfully, a man he was happy to get away from once he got to Paris, and after his Father`s death he had believed that he was free from the betrothal, but now his betrothed has come to Paris demanding his hand.

Athos is in love with D`Artagnan and is not about to let the Gascon become the property of this brutish oaf, leading to a LEGAL Duel for d`Artagnan`s hand to free him from this God Forsaken betrothal

Its kink meme lets just pretend that homosexuality was legal in the seventeenth century and men could be betrothed like women