Slytherin family

The Slytherin family was a pure-blood family with several notable members, particularly Salazar Slytherin, one of the four original founders of Hogwarts School of Witchcraft and Wizardry, who lived over one-thousand years ago and is the earliest known member of the House. Not much is known about this family, but it is possible that, like other families such as the Gaunts, who they are related to, that they had a tendency of marrying their cousins to keep their blood pure and to retain the traits of their ancestor, most notably the ability to speak Parseltongue. Many Dark wizards and witches came from this family, including Salazar Slytherin himself, and Lord Voldemort, whose death on May 2, 1998 marked the end of the line.

Early History
The Slytherin family was a prominent one in the wizarding world, as demonstrated by their famous ancestor, although over time their gene pool became unstable due to a habit of inbreeding, and they lost their wealth, which was completely non-existant by the time their last descendants, the Gaunt family, came to be.

Recent History
By the early twentieth century, when the family was extinct in the male line, Marvolo Gaunt, one of the last members, had only two children, Merope whom he abused and whose emotional trauma made it difficult for her to use magic, making others believe she was a Squib, and her brother Morfin, who spoke in Parseltongue more than English and frequently terrorized Muggles, eventually leading to his imprisonment in Azkaban.

Merope later ended the pure-blood line of her family by marrying a Muggle from the town near which her family lived, Little Hangleton, and having a Half-Blood son, Tom Riddle, who became the evilest dark wizard in history, known as Lord Voldemort. The female line of the Slytherin family continued for several years, ending with the death of Riddle, who neither produced any children or had any other known siblings or cousins.

Slytherin Family Tree
---             |                     |                   |    Antioch Peverell       Cadmus Peverell     Ignotus Peverell                  Salazar Slytherin |                                                |                                     |                                                 |                                     ---                                     |                                     |                                  Marvolo Gaunt   +   Mrs. Gaunt      Thomas Riddle   +   Mary Riddle |                          |                  |                                    -                                                         |                   |                             |                             Morfin Gaunt        Merope Gaunt       +           Tom Riddle Sr. |                             |                                                                       |                                                                Tom Marvolo Riddle

Salazar Slytherin
Salazar Slytherin was a great wizard of Medieval times. He was a Parselmouth (a wizard with the rare ability to speak with snakes), and skilled at Legilimency. He was one of the four founders of Hogwarts School of Witchcraft and Wizardry.

Tom Riddle
Tom Marvolo Riddle (December 31st 1926 - 2 May 1998), later known as Lord Voldemort, was the most powerful Dark Wizard in the history of the Wizarding world. He was born to Tom Riddle Sr., a wealthy Muggle who abandoned his wife and unborn child, and Merope Gaunt, a Pure-blood witch descended from Salazar Slytherin who died shortly after childbirth.

Born and raised in a dreary London orphanage and educated at Hogwarts School of Witchcraft and Wizardry, Tom was an exceptional pupil, being both a Prefect and Head Boy. Very few of the staff could have suspected his true nature, which manifested itself in several nasty instances during his adolescence of which Tom was never proven guilty, notably the opening of the Chamber of Secrets and the murder of the Riddles.

After leaving school, Tom briefly worked for Borgin and Burkes before disappearing for a long time. He absorbed himself completely into the Dark Arts, and underwent many extreme magical transformations, including the creation of several Horcruxes. He assumed the alias Lord Voldemort and gathered an army known as the Death Eaters, planning to take over the wizarding world and achieve immortality. This would result in two wars and a great many deaths, until Voldemort was finally defeated by Harry Potter during the Battle of Hogwarts. Tom Riddle's soul is now trapped in limbo, unable to move on or return as a ghost.

Other Families
The Slytherin family, like many of the pure-blood families, had some relation to many other families in the wizarding world. The Peverells, Gaunts, Blacks, Malfoys, Potters, Weasleys, Prewetts, and other families are all linked to one another through bloodlines and intermarriage.

The only known direct descendants from Salazar Slytherin were the Gaunts, who for the most part shared their ancestor's beliefs in the purity of wizard blood. They also spoke in Parseltongue between themselves. Tom Marvolo Riddle was the last descendant of the Gaunt family and spoke Parseltongue as well.

The Gaunt family was also descended from the Peverells, although it is unknown if one of the two infamous bloodlines preceded the other or if they simply merged at some prior point.

Heirlooms
The family held onto Salazar Slytherin's Locket for many generations, and in later years Marvolo Gaunt was in possession of a signet ring passed on from his Peverell ancestors. However, the locket left the family when Merope sold it to Borgin and Burkes in order to support herself while she was pregnant. It later came into the possession of Hepzibah Smith, who a teenage Tom Marvolo Riddle killed and stole the locket from. He also turned this heirloom of his mother's family into a Horcrux. Much later, it was stolen from its hiding place by Regulus Black, and later destroyed by Ron Weasley.

The ring, on the other hand, was also eventually turned into a Horcrux by Voldemort and destroyed by Albus Dumbledore with Godric Gryffindor's Sword. It also contained the Resurrection Stone.

Etymology
Slytherin may refer to the words "sly" as well as "slithering", which is the form of locomotion of snakes, possibly referring to their rare ability to talk to snakes called parseltongue.