Mary Wakefield has two brothers; Maximilian Wakefield (born 1967), an entrepreneur and racing car driver, and Jack Wakefield (born 1977), former director of the Firtash Foundation and an art critic who writes for The Spectator and other publications. A third brother, William Wakefield, was born in 1975 and died in infancy.
In December 2011, Wakefield married Dominic Cummings, a friend of her brother Jack Wakefield.
— Mary Wakefield (journalist)
It would seem far fetched to go as far as mentioning a brother who died in infancy, and fail to mention a by far more famous one, were the two to have truly been siblings; of ocurse, they could still, in theory, be (distant) cousins, or uncle and niece (of some degree), but, with over forty thousand people sharing this particular surname in the Anglosaxon world, it's not clear why one might expect these two, in particular, to be closer than any other such possible pairing; I myself happen to bear the same surname as one of my town's former mayors.