Joffrey Lannister
Joffrey Lannister, born Joffrey Lydden, was the first Andal-blooded King of the Rock, and the first man to bear the Lannister name without being born into that house.
He came to the throne of Casterly Rock not by conquest but by marriage, when a council chose to crown him after the previous king died leaving no male heirs.
Chapter 1
The first Andal of the Rock
Books only
Ser Joffrey Lydden married the only daughter of King Gerold III Lannister, lord of Casterly Rock. When Gerold III died leaving no male heirs, a council chose to crown his son-in-law.
On taking the crown, Ser Joffrey adopted his wife's surname and became Joffrey Lannister. He was thus the first lord of Andal blood to sit at Casterly Rock.