Yes, I think that's right that they would be first cousins, although I am not sure everyone agrees that Verlinda's maiden name was Cotton.Some people think it was Graves.Also, some people think that Verlinda might have been a second wife and was not the mother of all of William Stone's children.I copied this years ago from Vickie Kay Calvert's homepage:
Notes for Elizabeth Stone: A perusal of her father's will (see part 1) gives the impression that Elizabeth, seemingly the eldest child, and the recipient of special bequest, was the issue of a first marriage. The will of Verlinda, widow of Wm.Stone, dated 3 Mar. 1674/5, Charles Co.,Md.; proved 13 July, 1675, makes but three bequest: 1st, Benony Thomas heirs to whom she leaves 400 acres of land; 2nd, a daughter Doyen (Doyne), personalty; and 3rd, son John whom she makes her Executor, and beneficiary of the residue of her estate both real and personal, at 21 yrs. of age. Omitting mention of all but 2 of William Stone's children suggests that she may not have been the mother of the other children.