We meet this courtly squire early in Chrétien's Perceval: when Percivale first arrives at Arthur's court, Yvonet, holding a knife in his hand (he has obviously just been carving meat for the banquet), comes forward and points the King out to him.
As Percivale leaves to challenge the Red Knight of Quinqueroi, Yvonet follows him, eager to learn the outcome at first hand and bring the news back to court. Going alone (which may suggest he has slipped out secretly) and following paths he knows, he apparently arrives in time to witness the battle. Watching Percivale drag the Red Knight's body around trying to get the armor off, Yvonet enjoys a laugh (presumably good-humored) at his inexpertise, then helps him with the arms and armor, afterward carrying Arthur's cup and Percivale's message (about returning to avenge "Verrine") back to court along with word of how the fight went.
Much later in the same romance, when Gawaine sets forth to answer Guigambresil's challenge, he takes seven squires along with him. Chrétien makes the point that, although many fellow knights offer to lend him good horses and pieces of equipment, he takes only what is his own; presumably this includes the squires. We learn in line 5664 that Yvonet is one of them, not improbably the principal one. They accompany Gawaine as far as Escavalon, but, after undertaking the quest of the bleeding lance, he sends them home. They are mournful but obedient.
D.D.R. Owen remarks in a note that these two Yvonets are not necessarily the same character; I have failed to find any reason to suppose them different, unless it is the theory that Gawaine's adventures were originally meant to form a separate romance from Percivale's - and not even that would preclude the same squire Yvonet from appearing in both.
Chrétien leaves so many key charachters unnamed or very tardily named, that when he drops one in ready-named, I cannot help but suspect a figure already established in the chivalric literature of his time. Or even, perhaps, a living person known to the original target audience? Whatever the case, this Yvonet cannot be either of Uriens' sons, for they are both already knights, as Gawaine later explains to Queen Igraine.
Yonet greeted the innocent Perceval when Perceval first came to the court to be knighted. He supervised Perceval’s fight with the Red Knight, and - after Perceval won - he showed the young knight how to don the dead knight’s armor. His name is a diminutive form of Yvain and is used to describe the various Yvains in the Vulgate Merlin.
Yvonet li Avoutres
Ewein Avoutres, Uwaine Les Adventurous, Uwaine Les Avoutres, Yewains, Yvain les Avoutres, Yvain the Bastard; Yvains li Avoutres, - li Batarz; Yvonet li Avoutres, - l'Avoltre, - li Aoltres
King Uriens of Gore had two sons of the same name: Yvonet le Grand by Arthur's half-sister Morgan Le Fay, and Yvonet li Avoutres by the wife of Uriens' seneschal, according to Vulgate II. To try to keep things a little less confusing, I have used the more common present-day variant spelling Ywaine for the legitimate son, Le Grand (also called Le Blanchemains, etc.), and reserved the variant Yvonet for Li Avoutres.
Malory uses both brothers, but does not explain their birth history, which may lead to confusion. Both appear together on at least two occasions, once at the tournament at Castle Dangerous and once in company with Sirs Brandiles (Brandelis), Ozana, Agravaine, and Mordred in one of the interminable mix-and-match adventures that largely make up Malory's books of Tristram. Yvonet, or Uwaine les Avoutres as Malory calls him, was killed by Gawaine, ironically, while they were both on the Grail Quest. Happening to meet, they indulged in a joust, and my misadventure Yvonet was mortally wounded. Gawaine got him to an abbey, where he was unarmed and given the Sacrament.
Then Gawaine asked him what he was ... I am, said he, of King Arthur's court, and was a fellow of the Round Table, and we were brethren sworn together; and now Sir Gawaine, thou hast slain me, and my name is Uwaine les Avoutres, that sometime was son unto King Uriens, and was in quest of the Sangreal; and now forgive it thee God, for it shall ever be said that the one sworn brother hath slain the other.
Chrétien de Troyes lists Yvain the Bastard among Arthur's good knights in the list beginning line 1691 of Erec and Enide. He mentions him again in Perceval, when Queen Igraine asks Gawaine about King Uriens and his sons, and Gawaine tells her about both Yvains; the second is called "the Bastard" and has beaten every knight he has ever fought.
Both Yvains are considered extremely courteous, brave, and intelligent - aside from his own personal friendship for the first (legitimate) one, Gawaine seems to place them on a level.
Yvain | The Legend of King Arthur
Yvaine | The Legend of King Arthur
Yvonet | The Legend of King Arthur
Ywaine | The Legend of King Arthur