Character Analysis
Also known as The Gawains, the Orkney clan of Dunlothian is related to Arthur through Igraine (Arthur's mom, and Morgause's sister). So, Gawain, Agravaine, Gaheris, Gareth, and Mordred are Arthur's nephews. Plus, Mordred's also his (incest-begotten) son.
These brothers are tight, tight, tight. They're very clannish, and are quick to come to the aid of their family members. Even when they become knights of the Round Table, they still hang out all together, and are scared and suspicious and cause problems. In this sense, they're the juvenile delinquents of Camelot.
They've had a rather difficult childhood, with an absentee father (off fighting wars against Arthur) and a cold and distant mother (who also practices witchcraft), so they've really not had anyone else except each other. They're a bit wild and unmannered because of this.
Okay, "wild and unmannered" is dancing around the subject a bit. They're kind of like little sociopaths when they're younger: they haven't been taught empathy or how not to be cruel. The book also implies that they've gone hungry and have been neglected—the boys are too thin and wear threadbare clothing.
In fact, the boys are so neglected and so starved for their mother's attention that they will do practically anything to get it, including killing a majestic beast—a unicorn—and dragging its bloodied, severed head back to the castle as a gift for her. That'll get her attention! Alas, she just ignores them, and later has them whipped for their antics. Arthur and the narrator continually deflect blame from the G-boys for their actions, because they've had such a horrible upbringing from "that woman."