House of Gaunt

"…the Gaunts, a very ancient wizarding family noted for a vein of instability and violence that flourished through the generations due to their habit of marrying their own cousins. Lack of sense coupled with a great liking for grandeur meant that the family gold was squandered...left in squalor and poverty..."

- Albus Dumbledore

The House of Gaunt was a pure-blood family descended from Cadmus Peverell and Salazar Slytherin. 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. They lived just outside Little Hangleton.

Origins
The House of Gaunt was once a prominent, affluent family in the wizarding world, the last known descendants of Salazar Slytherin and of the Four Founders of Hogwarts in general. As stated above, the Gaunts inherited their ancestor's ability to speak Parseltongue. Like other pure-blood families of the time, they were supreme advocates of blood purity and inbred. However, by the twentieth century, mentally unstable members of the family had squandered the family's fortune and cost it much of its prestige among elite pure-blood circles.

Gaunt Family in the 20th Century
By the early twentieth century, the Gaunts had been reduced to poverty, possessing only a few old heirlooms, and generations of inbreeding made them violent and unstable. Marvolo Gaunt was abusive toward his daughter Merope, whose emotional trauma made it difficult for her to use magic, making others believe she was a Squib. Her brother Morfin spoke in Parseltongue more than English and frequently terrorized Muggles, eventually leading to his imprisonment in Azkaban.

Merope's son was the notorious Dark Wizard Lord Voldemort.

Upon the death of Morfin Gaunt, heir to the House of Gaunt, in 1943, the male line of the Gaunt family ended. The female line continued for another 55 years, ending with the death of Lord Voldemort. Neither of the two produced any children or had any other known siblings or cousins.

Gaunt 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

Heirlooms
Marvolo Gaunt was in possession of a signet ring passed on from his Peverell ancestors. This ring was eventually turned into a Horcrux by Voldemort and destroyed by Albus Dumbledore with Godric Gryffindor's Sword. It also contained the Resurrection Stone.

The Gaunts also held onto Salazar Slytherin's Locket for many generations. However, 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.

Etymology
The word gaunt is defined as "haggard, drawn and emaciated" and "bleak, desolate". John of Gaunt was a fourteenth-century English noble whose heir deposed a king and usurped the throne, possibly alluding to the Gaunts' descendant Voldemort attempts to overthrow wizarding Britain's government and rule it himself.