SIR GAWAIN

http://orgs.bsc.edu/arthur/knights.html
He called Gwalchmai the son of Gwyar, because he never returned home without achieving the adventure of which he went in quest. He was the best of footmen and the best of knights. He was nephew to Arthur, the son of his sister, and his cousin. -Kilhwch and Olwen in Guest, 107

Gawain, along with Bedivere and Kay, appears early in some of the earliest Arthurian writings. He appears in early Welsh poetry as Gwalchmai, Walwen, or Gauvain. In the different legends, he is consistently related to Arthur as a nephew, though his parentage is variable. The earlier legends seem to place more emphasis on performance in battle, as seen in the quote above from Kilhwch and Olwen, than the later romances. Some believe that the character of Gawain is derived at least in part from some forgotten Celtic sun god. Gawain's strength increases, according to some stories, with the sun, peaks at noon, and wanes as evening approaches.
The character of Gawain has evolved incredibly over time, however. In the earlier stories, he is seen as a brave, honorable knight, but by the romances he has become womanizing, vengeful, and impulsive. In the Stanzaic Le Morte Arthur, he vows to kill Lancelot for his dishonor to the queen, king, and his brother, Agravain:

'I'll not return to England till
He's hanged upon a tree
For while I live and my powers last,
There are folk who'll fight for me.'
The king spoke next, then every lord
Gave his opinion plain,
And each one advocated peace,
Yes, all except Gawain.
                       -lines 2680-2687

Perhaps the most well-known story about Gawain is the poem Sir Gawain and the Green Knight, in which Gawain's knightly virtues are tested by Bertilak, the lord of a mysterious castle deep in the forest. The story is famous for its symmetry, irony, and complex narrative structure.