In the earlier romances, Sir Gawain was the noblest and strongest of Arthur's knights before he was supplanted by Lancelot as a paragon of chivalry and courtly love. Gawain is the eldest of the sons of Arthur's half sister Morgause. There are five in all, and they run 3 to 2 in terms of nobility vs. dastardliness. We've known Mordred for some time and we Agravain last week. They cover the dastardly side of the family. To clarify things (or make them even murkier - we'll see) here is a chart of Arthur's extended family culled from Sir Thomas Malory's Le Morte d'Arthur and T.H. White's wonderful compilation of novels The Once and Future King.
Dame Ragnell's protean condition deserves explanation, which I think is best served in a tale. Below is a link to a modern translation of the 15th century Middle English poem, "The Wedding of Sir Gawain and Dame Ragnell." Some might recognize it as also the Wife of Bath's Tale from Chaucer's Canterbury Tales. It is one of my favorite stories to tell, and I am proud to have been hired to tell this story as a wedding present. Some do say it containeth the secret of a happy marriage.