"Leodogran, the King of Cameliard,

Guinevere was the legendary queen consort of King Arthur. The name Guinevere may be an epithet – the Welsh form Gwenhwyfar can be translated as The White Fay or White Ghost (Proto-Celtic *Uindā Seibrā, "white phantom" or "white fairy"; Brythonic *vino-hibirā). Additionally, the name may derive from "Gwenhwy-mawr" or Gwenhwy the Great, contrasting the character to "Gwenhwy-fach" or Gwenhwy the less; Gwenhwyfach appears in Welsh literature as a sister of Gwenhwyfar, but in her scholarly edition of the Welsh Triads, Rachel Bromwich suggests this is a less like etymology. Geoffrey of Monmouth renders her name Guanhumara in Latin.

Guinevere is most famous for her love affair with Arthur's chief knight Lancelot, which first appears in Chrétien de Troyes' Lancelot, the Knight of the Cart. This motif was picked up in all the cyclical Arthurian literature, starting with the Lancelot-Grail Cycle of the early 13th century and carrying through the Post-Vulgate Cycle and Thomas Malory's Le Morte d'Arthur. Their betrayal of Arthur leads to the downfall of the kingdom.

from Wikipedia

The Historia mentions the isle of Avalon, where Arthur went to recover from wounds after his last battle, and it tells of Guinevere's infidelity with Lancelot and the rebellion instigated by Arthur's nephew Mordred.

Guinevere = Guenhuuara (Geoff of Mon.) = Guennuvar ( Gildas) = Gwenhwyfar ( welsh)

Guinevere - daughter  of King Leodegrance (Welsh Ogyr Van ), 

wife of Arthur, 

lover of Lancelot, 

sister of Arianrhod.