Violet Clarke is described by Philip José Farmer in Tarzan Alive and Doc Savage: His Apocalyptic Life as one of two daughters of Monica Clarke, the other being Alice Clarke Raffles.
Alice, Violet, and Violet's husband Dr. Siger Holmes were all present to witness the Wold Newton Meteorite strike. Siger and Violet were the parents of Mycroft Holmes, ancestor of - among others - Sherlock Holmes.
Dennis Power has noted that Mr. Farmer credits Alice with more relationships than he does Violet, and does not give the latter the surname of 'Raffles', and concludes that the two were only half-sisters.