- "To think that Tywin's golden twins would turn out to be such a disappointment. What a shame..."
- ―Gerion mocking his brother's children's fate.
Lord Gerion Lannister is the youngest son of Lord Tytos Lannister and Lady Jeyne Marbrand as well as the current Lord of Casterly Rock and Warden of the West.
Born the youngest brother of Lord Tywin Lannister, Gerion wanted a life independent of his brother and this ended up with him organizing a voyage to Old Valyria in 291 AC in order to recover the long lost Lannister Valyrian steel sword Brightroar.
To the surprise of many who expected him to fail, Gerion successfully made his journey and recovered the sword as well as a lot of wealth, earning him the moniker of the Last Valyrian.
He married Lady Alysanne Hightower soon after and had three children by her - Tytos, Cyrelle and Gerold. He has an older bastard daughter by a lover named Briony - Joy Hill.
After the conclusion of the wars following Robert Baratheon's death, Gerion was named the new Lord of Casterly Rock.