Guinevere was King Arthur’s wife. Everyone knows that. But the role she plays has been embellished and augmented to the point that it’s actually not clear if she ever existed at all (assuming King Arthur existed at all, the exploration of which could fill a library).
“In the ancient Welsh Mabinogion (called Culhwch and Olwen), Guinevere is called ‘Gwenhwyfar’ or ‘Gwenhwyvar’. Her name may mean The White Phantom. Guinevere was the daughter of Gogrfan or Gogrvan or Ocvran. She is the wife of King Arthur. The tale also mentions that Guinevere had a sister, named Gwenhwyach.
The Mabinogion says that King Arthur had three sons: Gwydre, Llacheu, and Amhar. But there is nothing in the legend to indicate that they were Guinevere’s sons, too. Either King Arthur had another wife or partner, or, more likely, we can probably assume that they were her sons.” http://www.arthurianadventure.com/guinevere.htm
“According to Giraldus Cambrensis, the inscribed cross from the royal grave at Glastonbury named her as Arthur’s second wife. Nothing is known of this first wife. Since the only surviving drawing of the cross only depicts one side and, presumably, any allusion to the queen was on the other, the claim of Giraldus is unverifiable. Those who believe Arthur died and was buried at Glastonbury generally accept that Guinevere was buried with him.” http://www.pantheon.org/articles/g/guinevere.html
“Variously portrayed in literature, she is called the daughter of King Leodegrance (Lleudd-Ogrfan) of Cameliard by Malory, the daughter of King Ogrfan Gawr (the Giant) of Castell y Cnwclas (Knucklas Castle) by Welsh Tradition, the daughter of King Garlin of Galore by Germanic tradition, the daughter of a Roman noble by Geoffrey of Monmouth and wife of King Arthur by everyone. Her name is spelled differently depending on where you look. It can be either the traditional Guinevere, or Guenevere, or Guenievre, or Guenhumare or Ginevra. In Welsh, she is Gwenhwyfar; in Cornish, Jenefer.
In all cases, she is surpassingly beautiful and desirable, if morally lax from the time of the Vulgate Cycle (13th century) onward. She is either forced into or conceives and engineers an extra-marital relationship with Lancelot and is either condemned, according to law, or forgiven outright for her sins. She either was a willing accomplice to Mordred’s treachery against Arthur, as suggested in Wace and Layamon, or was forced into it against her will as stated in John Hardyng’s “Chronicle” (1457). Early mentions of Guinevere, in the Triads of the Island of Britain, give tantalising glimpses of her original relationship with Mordred: he is shown forcing his way into Arthur’s Court, dragging the Queen from her throne and striking her, but the reasons why are unknown. The incident may have been related to quarrels between Guinevere and her sister, Mordred’s wife, Gwenhwyfach, which are said to have been the eventual cause of the Battle of Camlann.” http://www.britannia.com/history/biographies/guinever.html
At least we know that the morally lax element is a later, French addition, and not part of the original Welsh story. Lancelot was added at that time as well (naturally), and as I’ve written elsewhere, according to the Welsh tradition, Arthur SURVIVES Camlann and his fight with Modred, so she is not to blame even for that (https://sarahwoodbury.com/the-lion-of-wales-series/the-fictive-and-historical-king-arthur/).
In the Welsh Triads, in fact, King Arthur has THREE wives named Gwenhywfar, which seems plainly impossible: “In the poem known as the Welsh Triad, King Arthur has three queens … and all three wives are named Guinevere or Gwenhwyfar. The first is called Gwenhwyfar, the daughter of Gwent (Cywryd); the second is called Gwenhwyfar, the daughter of Gwythyr son of Greidiawl; and the third wife is Gwenhwyfar, daughter of Gogfran or Gogrvan the Giant.
This must have made for complex marital relations in Camelot, or perhaps this story tells us something about the near universal (British and Irish) Celtic love for the number three. Such ancient British or Welsh legends may suggest that the three wives of King Arthur (the three Gwenhwyfars) form a sort of female trinity which encompasses the personification of Britain as a Lady, the Land of Britain as a Mother, and the Sovereignty of Britain as a Queen.
Guinevere or Gwenhwyfar, if this reading of the ancient legends is true, is more than simply a queen, she is also a triple goddess. And thus her marriage to King Arthur is necessary in that she bestows blessings upon him, through their sacred marriage.” http://www.arthurianadventure.com/guinevere.htm
Given that this is the ancient, Welsh tradition, from whence the legend of Arthur came, it leads one to question her existence at all. Although one could also conclude that a single Guinevere did once exist, married to Arthur, and as his legend grew and was shaped by the needs of the story-tellers, so did hers.