The elderly Mr and Mrs Riddle lived in the Riddle House with their only son, Tom Riddle Sr. Snobbish and rude, they were unpopular with the villagers in neighbouring Little Hangleton.
From the Story
Discovered in Book 4, Chapter 1, The Riddle House
"Mr and Mrs Riddle were found dead in the drawing room of their house fifty years ago, along with their son Tom. The police report on the bodies revealed that the Riddles' had not been poisoned, stabbed, shot, strangled, suffocated or harmed in any obvious way. The doctors did note that each of them had died with a look of terror upon their faces, as though they had been frightened to death."