Clegane (father of Gregor and Sandor)
Knight of Clegane's Keep
A Game of Thrones (mentioned)|
A Clash of Kings (mentioned)
After the seven-year-old Sandor was attacked by twelve-year-old Gregor, burning half his face in a hot brazier, for playing with a toy Gregor had discarded, their father explained away his younger son's injuries by claiming his bedding had caught fire.
He died in a hunting accident. It is implied he was actually killed by his son Gregor.