Tom Marvolo Riddle, who would later become Lord Voldemort, was born on New Year's Eve, 1926 to Tom Riddle Sr and Merope Gaunt. Through his mother, he is the last descendant of the famous ancient wizard Salazar Slytherin. Through his father, he is a descendant of the Riddles of Little Hangleton, a muggle family. His mother, Merope, had used a love potion means to persuade the elder Riddle to marry her. Later on when Merope stopped feeding the potion to Riddle, she and her unborn child were abandoned by Riddle.
One New Year's Eve night, Merope wandered into an orphanage in London when she suspected she was about to enter labour. After giving birth, Merope asked the matron to name her son Tom, after his father, and Marvolo, after his maternal grandfather, Marvolo Gaunt, and died within the hour.
In 1942, the summer before his fifth year at Hogwarts (or, as Dumbledore phrased it, in the summer of his sixteenth year), Riddle returned to Little Hangleton, hoping to meet his maternal grandfather, Marvolo Gaunt, and confirm that he was a descendant of the Gaunts, and, through them, Slytherin. Instead, he met his uncle Morfin, learning of his grandfather's death and his father's non-magical nature. He stole an heirloom ring from Morfin, and, upon learning that his father was still alive and had abandoned his mother, murdered him as well as his father's Muggle parents. He framed Morfin for the murders by modifying his memory so that Morfin believed he was the murderer. Morfin confessed this to the Ministry of Magic, and was eventually found responsible by trial. Frank Bryce, the Riddles' gardener, fell under suspicion from the muggle police, as the door to the Riddle House had not been forced and Bryce was the only person with keys to the house. The cause of death could not be determined, however, due to the fact that the Killing Curse leaves the victim lifeless with no signs of any struggle, wound, or medical problem, and Bryce was released, though he was regarded with suspicion by the other villagers until his death in 1994 at the hand of Voldemort. In this way, two men were blamed for the Riddle murders and Riddle kept the Gaunts' ring and returned to Hogwarts for his fifth year.