Ned Stark's squire and ward. Theon is technically a Stark hostage to guarantee Balon's good behavior after his failed attempt of independence. Theon has lived at Winterfell since he was 8 years old and has become quite close to Robb and the other Stark children. He has two older brothers ("Maron" and "Rodrik" in the books), both slain, and an older sister, Yara (Asha in the TV series).
During the War of the Five Kings, Robb sends him backto the Iron Islands to plead his father to form a alliance with the North against the Lannisters. However, Balon has other plans and decides to wage war on his own against the North. Having to choose between his adoptive family and his blood-bound family, he raids Winterfell to earn the respect of the Ironborn.