Cleos Frey

Ser Cleos Frey is a Recurring character in the second season of Game of Thrones. He was a member of house Frey, having been the eldest son of Emmon Frey and Genna Lannister, and thus a nephew of Tywin Lannister and a cousin of Cersei, Jaime and Tyrion.

History
Cleos was born at Casterly Rock, the seat of his mothers family. When he came of age, he squired for an unnamed knight and became one himself.

In the HBO show
In the HBO Game of Thrones series, Cleos Frey was renamed "Alton Lannister". Unlike his book counterpart, Alton is killed by Jaime Lannister in an attempt to escape his captivity. His mother, instead of being Genna Lannister, is instead "Cynda Lannister".