After Missy started stabbing the dalek in the sewers with the brooch she got from the Doctor "upon the birth of her daughter," it got me to thinking: what if this isn't the first time the Master/Missy has been female? What if, back in the First Doctor days (before the televised episodes, when Hartnell's Doctor wasn't an old man yet), an earlier female version of Missy was the Doctor's first wife? That would make her Susan's grandmother. It would also give an even stronger reason why the Doctor would send Missy his confession disk, and could explain why he's had a soft spot for the Master/Missy over the years. (He's gone out of his way to save the Master/Missy's life even after the Master/Missy has tried killing him.)
Just a thought.
Johnathan
Just a thought.
Johnathan