The most recent LostCousins newsletter links to another site with part of Kate Middleton's family tree.
This site is Anthony Adolph's website and this is descriptive text dealing with Kate Middleton's Olive Lupton (1881 - 1936) ancestral line which goes back via Fairfax ancestry to King Edward III of England. The site also gives Prince William's Fairfax ancestry, it says that Kate Middleton "... is his 18th cousin three times removed and he is her 15th cousin three times removed". I wonder if the Fairfaxes of St Boswells are related to the same Fairfax.
Interestingly, Anthony Adolph is one of her distant cousins.
The Daily Mail says that Kate Middleton and Prince William are 12th cousins once removed through a common ancestor, Sir Thomas Leighton.
You may like to read my earlier blog about Kate Middleton's family tree.