From A Wiki of Ice and Fire
|Gerold III Lannister
|Daughter of Gerold III Lannister
|The World of Ice & Fire (mentioned)
Ser Joffrey, a knight of House Lydden, was married to the only daughter of King Gerold III Lannister, who was of First Men ancestry. When the king died without male issue, Joffrey was crowned by a council and took the name of House Lannister.