Joffrey is believed to be the oldest son and heir of King Robert Baratheon and Queen Cersei Lannister, both of whom entered into a political marriage alliance after Robert took the throne by force from the Mad King Aerys II Targaryen. In reality, his father is Jaime Lannister, the queen's brother and the Lord Commander of the Kingsguard. He has a younger sister, Myrcella, and a younger brother, Tommen , both whom are also the product of Jaime and Cersei's incest.
Joffrey takes after his mother in terms of looks and personality, his blonde hair being a subtle clue that he isn't really a Baratheon, who famously always possess black hair even when one of their parents possesses blonde hair. He is usually accompanied by his sworn shield, the formidable Sandor Clegane, who is better known as the Hound. Even before he ascends to the Iron Throne, Joffrey is spoiled, arrogant, cowardly, and sadistic; however these traits are further exacerbated upon Robert's death and his ascension to crown