Youngest son of Lord Balon Greyjoy and Alannys Harlaw, and after the death of Rodrik at Seagard and Maron under the rubble of the south tower, the last of Balon's sons. Taken to Winterfell at the close of the Greyjoy Rebellion to be raised a ward and hostage of Lord Eddard Stark, he grew up in the company of Robb Stark and called him brother, though he never quite forgot that he was the ironborn boy among the wolves.
When the war came, Robb sent him home to Pyke to treat with his father for the use of the Iron Fleet. Balon would have no part of any king's son and sent him back instead with orders to harry the Stony Shore. Theon took Winterfell instead, the seat of the family that had raised him; lost it to Ramsay Snow soon after; and was carried off in chains to the dungeons of the Dreadfort, where he was broken and remade into a creature called Reek. He passed into the keeping of Stannis Baratheon's host in the snows outside Winterfell, neither prince nor turncloak now, and the maesters will not yet venture what name he will answer to when the song is done.