Four entries with the name Yvain.
Yvain
Le Chevalier au Lion, The Knight with the Lion
Son of Morgan Le Fay and King Urien. Knight of the Round Table.
I prefer to separate him from other Yvains by spelling his name Ywaine.
Yvain
A Knight of the Round Table who was the son of King Hervi.
Found in the romance of Yder, he may be identical to the original Yvain, with “Hervi” being a corruption of “Urien.”
Source
Yder | Early 13th century
Yvain
Yvonet
Yet another of Arthur’s knights, variously called “the Crooked,” “the Buck,” “the Deer,” and “the Shining.”
He fought in the Saxon wars and joined one of Gawain’s quests to find Lancelot.
Sources
Lancelot do Lac | 1215-1220
Vulgate Lancelot | 1215-1230
Vulgate Merlin | 1220-1235
Arthour and Merlin | Late 13th century
Yvain
A knight in Arthur’s service who was the son of the Soumière (Somiére).
Source
Les Merveilles de Rigomer | Jehan, mid to late 13th century