Lancel Lannister

Lancel Lannister is a recurring character in Game of Thrones. He is played by guest star Eugene Simon and débuts in the third episode of the first season. Lancel Lannister was the squire to King Robert Baratheon and ensured that Robert had plenty of wine during his final hunt. Following Robert's death he has begun sleeping with Queen Regent Cersei Lannister, his cousin, and has also been elevated to knighthood.

Background
Lancel Lannister is the son of Ser Kevan Lannister and the nephew of Lord Tywin Lannister, the head of House Lannister and Lord of Casterly Rock. He is the cousin of Jaime, Cersei and Tyrion Lannister. He is a squire to King Robert Baratheon.

Season 1
King Robert has Lancel pour wine for him whilst discussing old battles with Ser Barristan Selmy. Robery mocks Lancel's alliterative name, asking if his father had a stammer. Robert becomes annoyed when Lancel runs out of wine and sends him for more. At the Hand's tourney, Robert orders Lancel to prepare him for battle as he intends to fight in the melee. Robert's constant insults fluster Lancel and cause him to make mistakes. He orders Lancel out of the tent to find a 'breastplate stretcher' (a fictional device), which causes both him and Eddard Stark amusement, though Stark seems to feel sorry for Lancel.

Lancel accompanies Robert, Renly and Ser Barristan on a hunt, constantly giving Robert wine. He is present when Robert is mortally wounded by a wild boar. Varys insinuates that Lancel's readiness with the wine may have been deliberate in order to slow Robert's reactions.

Jaime is held prisoner by Catelyn and Robb Stark in the Riverlands. While Jaime is gone, Lancel is seen being sexually intimate with his cousin Cersei. He asks her a series of questions including wondering if war is exciting. Cersei is irritated and tells him to get back into bed.

In the books
In the Song of Ice and Fire novels Lancel is a squire who harbors ambitions to become a great knight. He is loyal to House Lannister. He has the gold hair and general good looks of the Lannisters, but is considered a poor copy of Jaime at best.