More erroneous information has been published about Richard Warren than any other Mayflower passenger, probably because he has so many descendants (note that all seven of his children grew up and married). It is time here to debunk many of the mistakes that have been published over the past hundred years.
Common mistake #1. Richard Warren's wife is not Elizabeth (Jewett/Jonatt/Juett) Marsh. This is easily disproven. Elizabeth (Jewett) Marsh was born in 1614, which makes her not only younger than Richard Warren's two oldest children, but also makes her only fourteen years old when Richard Warren died. [Mayflower Descendant 2:63].
Common mistake #2. Richard Warren is not a proven descendant of any royalty, whether it be Sir John de Warrene or Charlemagne. Richard Warren's parents have not even been identified, despite extensive searches in the records of England (see the Mayflower Quarterly, 51:109-112 for a summary of one such search).
The only concrete things we know about Richard Warren's ancestry are that he was a merchant of London--whether he was born there or not is an entirely different question. We also know that his wife was named Elizabeth. He had five daughters baptized in England somewhere, and perhaps the true records will some day be brought to light.
There is a Richard Warren who married an Elizabeth Evans on 1 January 1592/3 in St. Leonards, and a Richard Warren who married an Elizabeth Doucke on 1 November 1596 in Sidmouth, Devon. However, since Richard's first child was born about 1610, a marriage in 1592 or 1596 seems most unlikely.
The I.G.I. lists the following baptisms of Richard Warrens from its parish register abstractions (1570-1588):
1 January 1570, St. Columb Minor, Cornwall (son of Lawrence)
25 March 1571, St. Matthew Friday Street, London
20 January 1572, Bishops Nympton, Devon (son of Baldwine)
18 January 1573, Burbage, Leicester (son of John)
2 October 1576, Phillack, Cornwall (son of John)
9 August 1580, Sandy, Bedford (son of William)
24 January 1580, St. Peter Cornhill, London (son of John)
12 June 1580, St. Giles Cripplegate, London (son of John)
1 October 1581, Harrow on the Hill, London
26 January 1583, Haughley, Suffolk (son of George)
11 August 1583, Darford, Kent (son of William)
28 August 1585, Redruth, Cornwall (son of Benet)
12 April 1585, Abbey, St. Albans, Hertford (son of William)
2 March 1586, St. Mary, Stoke Newington, London (son of Robert)
25 December 1587, Shillington, Bedford (son of Robert)
3 September 1587, St. Andrew by the Wardrobe, London
As should be plainly obvious, there were many Richard Warrens in England. If the true Richard Warren is ever identified, it will almost certainly be because the baptisms of his five daughters which should be somewhere in England. There are a few other small clues which may aid researchers looking for records. First, early Charlestown settler Ralph Spague married Joanna Warren, daughter of a Richard Warren from Fordington St. George, Dorset. This Richard Warren died in Fordington, Dorset before 1638. And early Watertown settler John Warren was baptized in Nayland, Suffolk, England in 1585, and he apparently had an uncle named Richard Warren.
Richard Warren appears to have been a merchant, who resided in London, and became associated with the Pilgrims and the Mayflower through the Merchant Adventurers. Richard Warren participated in several of the early explorations made by the Pilgrims in 1620, while looking for a place to settle. He appears by land records to have been fairly well-to-do.
When he came over on the Mayflower, he left behind his wife and five daughters, planning to have them sent over after things were more settled in the Colony. His wife and daughters arrived in America in 1623, on the ship Anne.
Nathaniel Morton wrote in his book New England's Memorial, first published in 1669, the following about Richard Warren:
This year  died Mr. Richard Warren, who was an useful instrument and during his life bare a deep share in the difficulties and troubles of the first settlement of the Plantation of New Plymouth.
Richard Warren is an ancestor to many famous Americans. Among them are Presidents Ulysses S. Grant and Franklin D. Roosevelt; and Alan B. Shepard, Jr., the first American in space and fifth man to walk on the moon. A published lineage showing Winston Churchill as a descendant of Richard Warren has a questionable generation and is most likely in error. However, Winston Churchill does appear to be a descendant of Mayflower passenger John Howland's brother Arthur.
Robert S. Wakefield, Mayflower Families in Progress: Richard Warren for Four Generations (Plymouth: General Society of Mayflower Descendants, 1991).
Ruth Berg Walsh, "The Search for Pilgrim Richard Warren's Parentage," Mayflower Quarterly, 51:109-112.
Eugene Aubrey Stratton, Plymouth Colony, Its History and Its People, 1620-1691 (Salt Lake City: Ancestor Publishers, 1986).
Nathaniel Morton, New England's Memorial (Cambridge, 1669).
William Bradford, Of Plymouth Plantation, ed. Samuel Morison (New York: Random House, 1952).
Richard Warren's English origins and ancestry have been the subject of much speculation, and countless different ancestries have been published for him, without a shred of evidence to support them. Luckily in December 2002, Edward Davies discovered the missing piece of the puzzle. Researchers had long known of the marriage of Richard Warren to Elizabeth Walker on 14 April 1610 at Great Amwell, Hertford. Since we know the Mayflower passenger had a wife named Elizabeth, and a first child born about 1610, this was a promising record. But no children were found for this couple in the parish registers, and no further evidence beyond the names and timing, until the will of Augustine Walker was discovered in December 2002 by Edward Davies. In the will of Augustine Walker, dated April 1613, he mentions "my daughter Elizabeth Warren wife of Richard Warren", and "her three children Mary, Ann and Sarah." We know that the Mayflower passenger's first three children were named Mary, Ann, and Sarah (in that birth order), and that they were born c1610, c1612, and c1614, so this put the nail in the coffin and we can say with near certainty that Richard Warren of the Mayflower married in Great Amwell, Hertford to Elizabeth Walker, daughter of Augustine Walker. Additional research is currently being sponsored by MayflowerHistory.com to see if anything further can be learned about these families.