Theon Greyjoy

Theon Greyjoy is the youngest son of Lord Balon Greyjoy of the Iron Islands and the younger brother of Rodrik, Maron, and Yara Greyjoy.

Background
Following his father's failed rebellion against the Northern Throne, Theon is taken as a ward (initially hostage) to King Eddard Stark of Winterfell. After Eddard's execution in King's Landing, Theon pledges his loyalty to Eddard's eldest son, King Robb Stark, in the subsequent War of the Three Kings. Theon takes Winterfell for Robb, but eventually is betrayed by his own men, which leads to his capture by House Bolton. He is tortured and forced into servitude by Ramsay Snow, who turns him into a broken pet named Reek. Theon, however, redeems himself by helping Ramsay's wife (and Robb's sister), Sansa Stark, escape from Winterfell and find refuge with her cousin Jon Snow. The two later retake Winterfell, defeating Ramsay and House Bolton.