Life Of Kate MIddleton

In a study of the ancestry of Catherine, William Addams Reitwiesner uncovered that she shares ancestors with her husband Prince William; the closest relationship is via Prince William's mother and Catherine's father through a common descent from Sir Thomas Fairfax and his wife Agnes (or Anne) Gascoigne, daughter of Sir William Gascoigne and his wife, née Lady Margaret Percy. This makes the couple fifteenth cousins. Sir Thomas Fairfax and Agnes Gascoigne are through Catherine's great-grandmother Olive Lupton, daughter of a Leeds cloth merchant Francis Lupton and his wife Harriet (née Davis) – Fairfax being an ancestor of Lupton. In turn Lady Margaret Percy is descended from Edward III.
In his original publication of Middleton's ancestry, Reitwiesner uncovered circumstantial evidence, that has since been disproved, suggesting that Catherine and William were twelfth cousins once removed with common descent from Sir Thomas Leighton and Elizabeth Knollys, the latter a cousin once removed of Elizabeth I.