Martyn Lannister

Martyn Lannister is a character in the third season. Along his brother Willem, he's a squire in the Lannister army. Both are great-grandsons of the late Lord Tytos Lannister's brother.

He is fifteen years old in Season 3.

Season 3
Martyn, along with his brother Willem, is captured by the forces of House Tully led by Edmure Tully following the Battle of Stone Mill. He's kept hostage at Riverrun.

After Robb Stark visits Riverrun to attend the funerals of Lord Hoster Tully, Martyn and Willem are visited in their cell by Queen Talisa Stark, who tends to Martyn's wounded hand while Willem looks in silence. Martyn asks if its true that Robb can turn into a wolf at night and devours the flesh of his enemies.

In the books
In the A Song of Ice and Fire novels, Martyn and his twin brother Willem are sons of Ser Kevan Lannister and younger brothers of Lancel Lannister instead of being great-grandsons of one of Lord Tytos Lannister's brothers. Martyn is captured at the Battle of Oxcross.