Much has been made of the coalminers and tradesmen in Kate Middleton's family tree, but what about her royal links? Genealogist Patrick Cracroft-Brennan analyses her ancestry for Channel 4 News.

Prince William and Catherine 'Kate' Middleton. (Getty)

Much has been made of Kate Middleton's "middle class" background, but does she have any royal links?

Patrick Cracroft-Brennan, editor of the online reference work Cracroft's Peerage: "Yes, she has, but they are very distant. Her great-great-grandmother, Frances Elizabeth Greenhow, was the 10 x great-granddaughter of Sir William Gascoigne, a Yorkshire knight who died in 1487. He married Lady Margaret Percy, 4th and youngest daughter of Henry Percy, Earl of Northumberland.

"The Earl descended from King Edward III through both his parents. Prince Charles and the late Princess Diana both descend from Sir William Gascoigne and his wife Lady Margaret.

"This makes William and Kate fourteenth cousins once removed through his mother and fifteenth cousins through his father.

This makes William and Kate fourteenth cousins once removed. Patrick Cracroft

"Through her Gascoigne ancestry Kate is also an eighth cousin seven times removed to George Washington, first President of the United States, and a thirteenth cousin twice removed to the war time leader General George Patton.

"A descent from Sir William Gascoigne is one of the commonest "royal descents" in both Britain and the United States. The New England Historic Genealogical Society has estimated that up to 50 million Americans can trace their ancestry back to King Edward III.

"All of these people are related (albeit very distantly) to both Kate and Prince William."

Are there any surprising figures in Kate Middleton's family tree?

"Apart from her one royal descent, her ancestry is pleasantly normal. Her father's family were solicitors in Leeds for several generations, and there is a close connection with the Lupton family, well known for their involvement in Leeds as woolen manufacturers.

"There are several people 'in trade', which if not glamorous is at least dependable, and there are coal miners from the Durham coalfields. Social classes are very fluid in Britain and seeing an ancestry where the 16 great-great-grandparents range from lawyers to coalminers is not at all unusual in my experience."

Kate Middleton family coat of arms. (Reuters)

How unusual is this union?

"Since the time of the Norman Conquest in 1066 it has been the norm for our kings to marry princesses from other European royal families. In many ways this was a good practice as it ensured that the Queen would not favour her family at court.

"Henry, Duke of Hereford, was already married to Lady Mary de Bohun when he seized the throne from his cousin in 1399 and became King Henry IV. His second wife was a French princess. King Edward IV broke the rule by marrying Lady Elizabeth Wydville in 1464. His brother, King Richard III, had already married Lady Anne Neville before he killed his nephew in 1483 and usurped the throne.

This union is very unusual in that it is the first time in British history that someone in direct line to the throne has married someone who was not either a foreign princess or came from a British aristocratic or titled family. Patrick Cracroft

"King Henry VIII had six wives - two of these were foreign princesses, the others were English aristocrats.

"King James II had married Lady Anne Hyde in 1633, well before he succeeded his brother, King Charles II. After her death in 1671 his second wife was an Italian princess.

"We then have to jump to 1923 and the marriage of the Duke of York and Lady Elizabeth Bowes-Lyon, the Queens parents, before we again have an aristocratic commoner marrying a future king. The Prince of Wales, Prince William's father, has famously married two aristocratic 'gels'.

"This union is very unusual in that it is the first time in British history that someone in direct line to the throne has married someone who was not either a foreign princess or came from a British aristocratic or titled family."

William & Kate's future children will become heirs to the throne. But who will they be leapfrogging?

Every child they have will move every other member of the royal family down a notch in the line of succession. Genealogists seem to have a passion in creating tables that show the succession to the throne in the minutest detail. Queen Victoria has thousands of living descendants, all of whom if not Roman Catholic or illegitimate are in the line of succession.

Is William 'more royal' than his father?

"You cant really say that. Prince Charles descends from a long direct line of British, Scottish, English, Norman and Saxon kings, stretching back quite literally into the mists of time. He is, to coin a phrase, as royal as they come.

"A lot of his ancestry through his father and his mothers father is 'foreign royalty' which through various cousin marriages has reinforced his descent from the Hanoverian kings.

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"The Queen's parents were distantly related, but no closer than Prince William and Kate are. The Prince of Wales's marriage to Lady Diana Spencer introduced new albeit illegitimate lines of descent from the later Stuart Kings of England and Scotland."

What titles does Kate Middleton acquire by marrying Prince William?

"As things stand at the moment, Kate will become "Her Royal Highness The Princess William of Wales".

"It is widely forecast that Prince William will be made a Royal Duke on the morning of his wedding, in which case Kate becomes 'Her Royal Highness The Duchess of X'.

"There are a number of ducal titles that are traditionally used by the Royal Family. Edinburgh, Cornwall, Rothesay, York, Gloucester and Kent are all in current use, Cumberland, Teviotdale and Albany are not available, so the chances are it will be either Cambridge, Clarence, Sussex, Strathearn or St Andrews.

"She will become the second highest ranking lady in the land after the Queen, so she will outrank all the ladies in the Royal Family apart from the Queen and the Duchess of Cornwall."

Patrick Cracroft-Brennan is the editor of Cracroft's Peerage - a guide to British peerage, baronetage and an online database for family history researchers.