Ancestry charts of Diana Spencer and Catherine Middleton

All people are descended via various racial or ethnic lines of antiquity, but in most cases, records do not exist. The British Royal Family is one of the few families for which ancestry can be traced to many notable lineages of antiquity. Their lineage can be traced back to the Saxons, Scottish (Stuart dynasty), Welsh (Tudor dynasty), Irish, Germans (Hanover and Windsor), French (Norman and Angevin), Russians, Franks and perhaps even Byzantines.

Ancestry
Diana, Princess of Wales (née Diana Spencer) was born into a British noble family. Her ancestry includes many royals and nobles.
 * Her father, John Spencer, 8th Earl Spencer, descended from over a dozen monarchs:
 * King James II of England (7x great grandfather of John Spencer)
 * King Charles II of England (7x great grandfather of John Spencer)
 * Through his illegitimate son, Henry FitzRoy.
 * Potentially through Mary Crofts (Mary Stuart), who claimed Charles II was her father by mistress Lucy Walter. This paternity was not acknowledged by the King. Other sources list Theobald Taaffe, 1st Earl of Carlingford or Henry Bennet, 1st Earl of Arlington as her father. The surname Crofts comes from Bennet's mother.
 * King Charles I of England (father of Charles II and James II of England)
 * King Henry IV of France (maternal grandfather of Charles II and James II of England)
 * Ferdinand I, Holy Roman Emperor (2x great grandfather of Charles II and James II of England)
 * King Philip I of Castile (father of Ferdinand I, Holy Roman Emperor)
 * Queen Joanna of Castile (mother of Ferdinand I, Holy Roman Emperor)
 * King Ferdinand II of Aragon (father of Joanna of Castile)
 * Queen Isabella I of Castile (mother of Joanna of Castile)
 * King John II of Castile (father of Isabella I of Castile)
 * King Henry III of Castile (father of John II of Castile)
 * King John I of Portugal (great grandfather of Isabella I of Castile)
 * King Edward III of England through two of his sons: Lionel of Antwerp, 1st Duke of Clarence and John of Gaunt, 1st Duke of Lancaster
 * Through a daughter of Lionel of Antwerp, Philippa of Clarence (17x great grandmother of John Spencer)
 * Through a daughter of John of Gaunt, Philippa of Lancaster (wife of John I of Portugal and great grandmother of Isabella I of Castile)
 * Through a daughter of John of Gaunt, Catherine of Lancaster (wife of Henry III of Castile and mother of John II of Castile)
 * Through a daughter of John of Gaunt, Joan Beaufort (18x great grandmother of John Spencer through daughter Eleanor Percy)
 * Also through her father, John Spencer, she descended from Rory O'Moore, an Irish noble, through his grandson, William Sarsfield. William's brother was Patrick Sarsfield (who was named after their father).
 * Her mother, Frances Roche, was the daughter of an Irish peer, Maurice Roche, 4th Baron Fermoy.

Catherine, Duchess of Cambridge (née Middleton) is descended from King Edward IV through her mother, Carole Middleton, and from King Edward III through her father, Michael Middleton. She therefore shares a number of common ancestors with her husband, Prince William:
 * According to genealogists Patrick Cracroft-Brennan and Anthony Adolph, Catherine is a direct descendant of King Edward IV, via her mother Carole Middleton, from Elizabeth Plantagenet, (King Edward IV's illegitimate daughter by Elizabeth Lucy), via Sir Thomas Blakiston Conyers, 9th Bt. of Horden, Durham. Thus, Catherine and Prince William's closest common ancestors are Sir William Blakiston of Gibside Estate and his wife Jane Lambton, making them eleventh cousins once removed.  These findings echo Christopher Challender Child's research, published in 2011.
 * It was reported in December 2014 that the famous Blakiston-Bowes Cabinet, held at the Metropolitan Museum of Art, provided proof that Catherine shared ancestry with Queen Elizabeth, the Queen Mother. Catherine and the Queen Mother share a common ancestor, County Durham's Sir William Blakiston, whose great granddaughter, Elizabeth Blakiston, married into the Bowes-Lyon family who were ancestors of the Queen Mother, née Lady Elizabeth Bowes-Lyon. The cabinet was made in Newcastle to celebrate the union of the two gentry families. Reports suggested that Catherine and the Queen Mother's blood cousinship was the reason why Catherine wore the Queen Mother's tiara when she wed Prince William.
 * Genealogical research by William Addams Reitwiesner, also published in 2011, found that Catherine is descended from Sir Thomas Fairfax (c.1475–1520) and his wife Agnes Gascoigne, an ancestor of Diana, Princess of Wales, and a descendant of King Edward III, via Michael Middleton's grandmother Olive Middleton née Lupton. This ancestry makes Catherine and Prince William fourteenth cousins once removed.

Common ancestors:
 * They both descend from King Edward III through his sons, Lionel of Antwerp's, daughter Philippa of Clarence and through another son's, John of Gaunt, daughter Joan Beaufort. Shared medieval ancestors (between Diana and Catherine) include  Margaret Percy (great granddaughter of Joan Beaufort and 2x great granddaughter of Philippa of Clarence) and Sir William Gascoigne (2x great grandson of Joan Beaufort).
 * Diana and Catherine also share a number of other common ancestors including: Sir William Blakiston, Anne Gascoigne (daughter of Margaret Percy and William Gascoigne) and her husband, Sir Thomas Fairfax.

Ancestry chart from Edward III

 * Sir William Gascoigne is a 2x great grandson of Joan Beaufort. His mother, Joan Neville, is daughter of John Neville, who is son of Mary (Margaret) Ferrers, a daughter of Joan Beaufort. On his father's side, he is a 2x great grandson of William Gascoigne (father's father's father's father, all named William Gascoigne).