|Born||In 211–219 AC|
|Died||In 236 AC, at the Wendwater|
|Book(s)||The World of Ice & Fire (mentioned)|
Tion was the second-born son of Gerold Lannister, Lord of Casterly Rock, and Lady Rohanne Webber, his second wife. He became the heir to Casterly Rock after his older twin brother, Tywald, died in the Peake Uprising in 233 AC. According to a semi-canon source, Tion was the squire of Prince Aegon Targaryen during the conflict.
Betrothal and marriage
Tion had been betrothed to a daughter of Lord Rowan. However, after his twin brother Tywald died, Tywald's betrothed, Ellyn Reyne, convinced him to espouse her instead. While Lord Gerold opposed the match, in the end, he gave way, and Tion and Ellyn became betrothed. According to semi-canon sources, Lord Gerold agreed to the match when Tion told his father how Tywald, with his last words, had pleaded with Tion to “take care of Lady Ellyn”. In 235 AC, Tion and Ellyn were married at Casterly Rock. In the same ceremony, Tion's younger brother Tytos was married to Lady Jeyne Marbrand.
Fourth Blackfyre Rebellion
In 236 AC, Daemon III Blackfyre began the Fourth Blackfyre Rebellion. This rebellion did not last long, and the royalists lost fewer than one hundred men during the Battle of Wendwater Bridge. Ser Tion, however, was one of the deceased.
Tion's widow, Ellyn, had been quite influential as the future Lady of Casterly Rock, but with Tytos Lannister now the heir to Lord Gerold's seat, Ellyn's power dwindled. According to semi-canon sources, Lady Ellyn made one final attempt to cling to her place. She declared that she was pregnant with Tion's child. However, months went by and her belly remained flat, proving her words untrue.