Lyanna Stark

Princess Lyanna Targaryen of House Stark is the only daughter of Lord Rickard Stark and his wife, Lyarra Stark. She was married in secret to Prince Rhaegar Targaryen and is the mother of Jon Snow, though he is unaware of this. Her sudden disappearance and breaking her betrothal with Lord Robert I Baratheon was what started Robert's Rebellion, which killed her elder brother, her father, and her husband. Lyanna died in childbirth in the Tower of Joy.