Tom Riddle Senior

"Within a few months of their runaway marriage, Tom Riddle reappeared at the manor house in Little Hangleton without his wife. The rumor flew around the neighbor­hood that he was talking of being 'hoodwinked' and 'taken in'... He left her, never saw her again, and never troubled to discover what became of his son."

- Albus Dumbledore on Tom Riddle

Tom Riddle Sr. (1905-1943) was an affluent Muggle who lived in the town of Little Hangleton. He was the son of the wealthy Muggle couple Thomas and Mary Riddle. Tom was married for a short time to Merope Gaunt and was the father of Tom Marvolo Riddle, also known as Lord Voldemort, who killed his father when he was sixteen in retaliation for Tom's abandonment of his wife and unborn child.

Admiration from Afar
"She likes looking at that Muggle. Always in the garden when he passes, peering through the hedge at him, isn't she? And last night — hanging out of the window waiting for him to ride home, wasn't she?... I got him as he went by and he didn't look so pretty with hives all over him, did he, Merope?"

- Morfin Gaunt on Merope's infatuation with Tom Riddle

Thomas, Jr. lived in a luxurious manor house not far from a run-down cottage that was home to the Gaunts, a wizarding family descended from Salazar Slytherin and Cadmus Peverell. Merope, who led a miserable life of poverty and abuse at the hands of her father and brother, became infatuated with Tom, watching him ride by on his horse, sometimes in the company of a woman named Cecilia.

When her brother Morfin noticed her interest, he hexed Tom with hives. The Ministry of Magic discovered this, among other incidents, and presumably performed a Memory Charm on Tom. They also arrested Morfin and Marvolo Gaunt, and both wizards were sentenced to Azkaban. While they were gone, Merope made her play for Tom.

Marriage
It was speculated by Albus Dumbledore and Harry Potter that Merope used either the Imperius Curse or a love potion to attract him, though it is possible that he married her of his own free will. In any case, the two married, despite public disapproval over "the squire's son running off with the tramp's daughter". It is unclear whether Tom believed himself to be in love with Merope at the time, or if he married her because she became pregnant.

In any case, eventually Merope stopped whatever enchantment she had used on Tom in the hopes that he had truly fallen in love with her since, or would at least remain with her for the sake of their unborn child.

Abandonment
"Tom Riddle left her while she was still pregnant... I believe that Merope, who was deeply in love with her husband, could not bear to continue enslaving him by magical means. I believe that she made the choice to stop giving him the potion. Perhaps, besotted as she was, she had convinced herself that he would by now have fallen in love with her in return. Perhaps she thought he would stay for the baby's sake. If so, she was wrong on both counts."

- Albus Dumbledore

Thomas,Jr. reacted with shock and horror to the truth of his relationship with Merope, and fled back to Little Hangleton. He claimed to have been "taken in" by Merope, which may have been an allusion to her being a witch, or to her methods of attracting him. Rumours in the town claimed that Merope had lied about being pregnant. Riddle's son himself came to believe that his father abandoned Merope solely because he discovered she was a witch.

Whatever the reason, Riddle abandoned his wife, and she was left alone and impoverished in London. Soon after, she gave birth to a son she named Tom Marvolo Riddle, after the baby's father and Merope's own father, Marvolo Gaunt. Merope died shortly after giving birth and the child was left in the care of a Muggle orphanage.

Patricide
In 1943, sixteen-year-old Tom Marvolo Riddle, who would later take on the alias Lord Voldemort, ventured to Little Hangleton to investigate his heritage. He learned the details of his parents' union from his uncle Morfin Gaunt and sought revenge on what he saw as the man who caused his mother's death. Tom Marvolo Riddle murdered his father and paternal grandparents with the Killing Curse and framed Morfin for the crime.

It is unknown if any words were ever exchanged between father and son, although it seems likely, given that Thomas Riddle Jr. and his parents were found with looks of utter terror frozen upon their faces. The adult Lord Voldemort would later reminisce to Harry Potter that his father "didn't like magic" while gazing up at the Riddle House from the Little Hangleton graveyard, something Voldemort could only have known if he had spoken directly to Thomas Riddle Jr. himself. The younger version of Voldemort from his old diary also remarked to Harry Potter in the Chamber of Secrets that his father had deserted his mother after discovering she was a witch. This would again further evidence the possibility that Riddle likely spoke with his father about these matters prior to performing the curse that sealed Tom Riddle Jr.'s fate.

Tom Riddle Sr.'s murder was used by his son to transform Marvolo Gaunt's Ring into his second Horcrux. Voldemort seemed to see this murder as retribution for the miserable existence his father had condemened him to in his abandonment, as well as his own triumph over his "filthy Muggle" heritage. Voldemort made use of his father's murder again in 1995, when he used a bone from Tom Riddle Jr.'s grave to make the Potion that resurrected him.

Personality and Traits
Little is known about Tom Riddle Jr., but some things can be inferred. He seems to have been something of a snob and rather callous. For example, when he and Cecilia were riding by the Gaunt Shack on one occasion, Bob Ogden ran out, having been terrorized by the Gaunts, and stumbled into Tom Jr.'s horse. Both he and Cecilia "roared with laughter" at this. Very handsome and wealthy, Tom, Jr. boasted to his companion about how much property his family owned. Tom also abandoned his pregnant wife and apparently made no attempts to find out what happened to his child.

Appearances

 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * ''Harry Potter and the Goblet of Fire
 * ''Harry Potter and the Goblet of Fire (film)
 * ''Harry Potter and the Half-Blood Prince