C
I remember seeing a theory about crocodile's secret turning out to be about him being a former royal that revolted against his family.
Doflamingo will eventually join cross guild alongside hancock, moria and weevil so the "company" will be full of people who are either royals by blood and/or by title.
If mihawk is actually from a royal family then he could have a story with them, similar to doffy's that made him become a pirate.
Personally, i'm not a fan of the whole betrayal thing because it has been used so many times that at this point it feels a little cheap.
I would rather have mihawk's betrayal revolving around his life as a pirate then his past as a noble/royal.