The Thorne/Dorne family can be traced back to Edmund Dorne, Esq. of Northamptonshire. He was born about 1420.  We don't really know much about his ancestors. Edmund was never knighted but he was quite successful in life. His name is found in the records of the time, on land deeds and in court cases. Edmund made a very advantageous marriage to the Widow Margaret Billings Lovatt.  The marriage was most likely arranged by parents or family members, love had little to do with medieval marriage. If you've never read The Paston Letters, I highly recommend it. The letters, written by members of the Paston family in the 15th century, open a window into their world and daily life. This would be the same time period as Edmund and Margaret. Margaret Billings' father was actually mentioned in one of their letters.
Margaret was the daughter of Sir. Thomas Billing of Northamptonshire. The ancestry of Sir Thomas is unknown, it is believed that his beginnings were modest.  He trained as a lawyer and was a member of Gray's Inn. His career was centered mostly in London and where he fulfilled many important civic duties. including that of Common Sergeant and Under Sheriff. He served as a member of Parliament for both Northamptonshire in 1445 and for London in 1449.
As the century progressed the country was convulsed by the tumultuous events now known as the "War of the Roses." The 'war' was the protracted fight for the English throne between the House of York and the House of Lancaster and it forced many to choose sides. In the early 1450's Thomas Billing was retained as a lawyer for the Lancastrian Queen Margaret of Anjou. In the parliament of 1459 he was one of the crowns legal adviser who drew up the bill of attainder against the rebellious Duke of York. In 1460 a decisive battle was fought at Northampton. The victorious Yorkist had taken up a defensive position at the Delapre Abbey. It is possible that Thomas Billing switched allegiance as he was reappointed King's Sergeant by the new King.
Thomas was, at the height of his career in 1469, the Chief Justice of The King's Bench. It is thought that he participated in the trial of the Duke of Clarence, brother of King Edward. He, Clarence, was found guilty and supposedly executed by being drowned in a butt of Malmsey wine. Thomas was finally knighted in 1475. He remained Chief Justice until his death in 1481. Of course, by 1485, Henry Tudor had captured the throne and set the stage for the glorious Tudor period in England. 
Thomas was married twice; his first wife was Katherine Gifford. Their daughter Margaret was born about 1430. Margaret was also married twice. She was first married to Nicholas Lovatt, the son and heir of Thomas Lovatt I. They had one child, a son, who was his grandfather's heir. Thomas Lovatt I was quite wealthy and his grandson became a substantial landowner in Northamptonshire.
edmund and margaret
Edmund and Margaret were married some time before 1455 when they were both named in a land deed from her father in Law, Thomas Lovatt. The land was given to Edmund and Margaret, but would revert to Margaret's son Thomas Lovatt on her death. Margaret and Edmund had at least four children, sons Roger, Thomas, John and William. Thomas and John were mentioned in their half brother's will in 1491.
In 1471 Margaret Lovatt, named for her grandmother Margaret Dorne, was contracted to marry John Brooks of Great Oakley. Prior to the marriage a complicated land deal was worked out with John's father William and his wife Dowce Billing Lovatt, a cousin of Margaret Dorne. William Brooks exchanged manors and land at Astwell, Falcote, and land in Wappenham, amounting to about 2170 acres and the Dornes and Lovatts gave him land in Ruston, Great Oakley and other land once belonging to Thomas Lovatt I. Margaret Dorne and her heir were given the Manor of Astwell which became the family seat of the Lovatt Family whose descendants eventually became the Earls of Ferrers. 
thomas and alice
Edmund's second son Thomas, b. abt. 1455 married Alice Arden of Cottesford and Kirtlington, Oxfordshire. Thomas died before 7 October 1502. He was called Thomas of Syresham in 1501 and Thomas of Myxbury in 1502 when a writ called a "diem clausit extremum" was written. The term means 'he closed his last day' and is written after a inventory of his estate was done. 
Alice was the daughter of William Arden of Cottesford and Agnes Stotesby of Evenley. Williams father was identified as Robert Arden of Cottesford. His widow Alice remarried by 1512 to William Woodward.  After Thomas' death, Alice remarried to a William Woodward.
william and alice
William was born about 1485, probably at Syresham. He married Alice, possibly Alice Stotesbury before 1515. He wrote his will in 1529 but it was not proved before 1537. The first mention of him in the records is when he was noted to owned suit at the manorial court of Syresham, previously held by his father in 1508. On 22 May 1537 he again owed suit at the manorial court of Syresham whose overload was Magdalen College at Oxford University. But, by then he also owned land in Yardley-Hastings. He seems to be the first of the Thornes with land in that area. In 1531 it was recorded that he was patron of the living at Yardley-Hastings, meaning it was his right to appoint the vicar at the church.
In his will, William named his wife Alys, leaving her 'certain lands'. All his Copyhold lands in Yardley and in Syresham he left to his son Thomas.
thomas and mary purefoy
Thomas was born about 1521 based on the birth of his children. When he wrote his will in 1588 he made his home in Yardley-Hastings. He married Mary Purefoy by about 1550. He and Mary were the parents of Susanna Thorne, wife to Roger Dudley and mother to Thomas Dudley.
 Brandon, Fradd, "Ancestry of Thomas Thorne, Granfather of Thomas Dudley," The Genealogist vol 19 no 1 (Spring 2005).
 Robert Edmund Chester Waters, Genealogical Memoirs of the Extinct Family of Chester of Chicheley: Their Ancestors and Descendants, Volume 1, (London: Robson and Sons, 1878)
 Nigel Ramsey, "Sir Thomas Billing," Oxford Dictionary of National Biography (www.oxforddnb.com : accessed 28 April 2016).
 Ramsey, "Sir Thomas Billing."
 Ramsey, "Sir Thomas Billing."
 Waters, Genealogical Memoirs.
 Fradd, "Ancestry of Thomas Thorne".
 Fradd, "Ancestry of Thomas Thorne".
 Charlotte Carmichael Stopes, "The Warwickshire Ardens," The Genealogical Magazine Vol. 2 (1899) 154, digital images, Google Books (https://www.books.google.org : accessed 1 May 2016).
 William Harvey, John Philipot, William Ryley, The Visitations of the County of Oxford Taken in the Years 1566, (London: publisher not noted, 1871) 207, digital images, Google Books (https://www.books.google.org : accessed 1 May 2016).