In following your lead regarding the possibility of John Mitchison being the father of William, husband of Lucretia. I found 1 tidbit of info in the IGI. John Mitchison b. 15 Feb 1721 Saint John's Parish, Prince George's Co., MD f: John Mitchison m: Constant Source:Index to the register of births, marriages and deaths in St. John's or Piscataway Parish, Prince George's CountySt. John's Parish (Prince George's County, Maryland : Episcopal) NOTE: This would put the father, John Mitchison Sr at the same place and time as your John Mitchison leasing land 10/10/1717 This might make John, b 1721, brother to William.