a Sherlock question

Question to British Sherlock fans: Assuming the characters aren't fiction in the Sherlockverse, is it plausible that Sherlock and Mycroft could be grandsons of Charles and Lady Mary (née Wimsey) Parker? Or are the class markers all wrong for grandnephews of a Duke?

(Given that I've read speculation on original canon's Holmes being related to Peter Wimsey, I can't resist speculating on the same for the new version.)