Theon Greyjoy

Balon Greyjoy's last living son, handed over as hostage and ward when Pyke fell and his father bent the knee. He was raised at Winterfell in Eddard Stark's household — well treated, by all accounts, and never for a moment allowed to forget what he actually was.

Robert's terms were, by the standards of the age, merciful: Balon kept his islands and his life and lost a son to another man's hall. It was also a decision that quietly guaranteed a boy would grow up belonging fully to neither house, which is the sort of long consequence Robert never once considered.