The ‘Sacred Twenty-Eight’ would be embraced by Voldemort, despite being a half-blood himself, and sneered at by wizards who recognised that the wizarding world would have died out if their ancestors hadn’t married Muggles.
Abbott – A grave belonging to an unknown Abbott was found by Harry in Godric’s Hollow. Hannah Abbott was the first of her year to be Sorted and Hannah herself fought bravely during the Battle of Hogwarts.
Avery – Mentioned by surname only in the Harry Potter books. An Avery had just stepped out of the room at the Slug Club party where Tom Riddle asked Professor Slughorn about Horcruxes. A Death Eater named Avery was also part of the ambush at the Department of Mysteries. He was believed to have ‘wormed his way out of trouble’ following Voldemort’s first defeat, by claiming to have been acting under the Imperius Curse.
Black – Sirius, Harry’s godfather, was the first of the Black family not to gain admittance to Slytherin. He later gave his family’s London house over as headquarters for the Order of the Phoenix, much to the chagrin of the spirits of his ancestors who haunted it. His brother was Regulus Black, a Death Eater who switched sides and tried to destroy a Horcrux, and among Sirius’s many cousins were Bellatrix Lestrange and Narcissa Malfoy.
Bulstrode – A particularly unpleasant Slytherin and early consort of Draco Malfoy, Millicent Bulstrode had a number of skirmishes with Hermione. The latter had a mishap with some Polyjuice Potion and one of Millicent’s cat’s hairs.
Burke – Caractacus Burke, one of the founders of sinister wizarding shop Borgin and Burkes, was seen by Harry in the Pensieve, buying Salazar Slytherin’s locket from Voldemort’s mother when she was left destitute and pregnant.
Crouch – Bartemius Crouch might have led a very ordered life were it not for his Azkaban-escapee and Death Eater son ‘Barty’ Jnr, who killed him and transfigured his body into a bone. Barty used Polyjuice Potion to impersonate Mad-Eye Moody to lead Harry into the Triwizard Tournament trap.
Fawley – No members of this pure-blood family are mentioned in the Harry Potter stories.
Flint – Slytherin Quidditch captain Marcus was a member of the Flint family who lived up to his sharp, spiky name.
Gaunt – Quite where Voldemort got his meanness from is indicated from the portrait Rowling painted of his grandfather, Marvolo Gaunt, and his uncle Morfin. Obsessed with their own pure-blood status and with being the only living descendants of Salazar Slytherin, they terrorised Voldemort’s mother Merope and accused her of being a Squib. After a string of attacks on Muggles, the two Gaunt men ended up in Azkaban, leaving Merope alone to enchant local Muggle boy Tom Riddle – and we all know that didn’t end well.
Greengrass – Daphne Greengrass was a student alongside Harry, Ron and Hermione who only made one appearance in the books. Draco Malfoy went on to marry Astoria Greengrass, a woman more tolerant of Muggles than her in-laws would have liked.
Longbottom – Neville Longbottom was one of Harry, Ron and Hermione’s best friends and a fellow Gryffindor. He was raised by his grandmother Augusta because his Auror parents had been so badly tortured by the Lestranges that they were confined to St Mungo’s Hospital for Magical Maladies and Injuries. Longbottom killed Voldemort’s snake Nagini during the Battle of Hogwarts, playing a major role in the downfall of the Dark Lord. He later became Hogwarts Herbology professor.
Malfoy – The fate of this long-standing dynasty might have ended had Draco Malfoy and his parents, Lucius and Narcissa, not decided to switch sides during the Battle of Hogwarts. The pure-blood Malfoy went on to marry Astoria Greengrass and had a son, Scorpius.
Nott – ‘Weedy-looking’ Theodore Nott was a contemporary of Harry’s at Hogwarts whose father was one of the Death Eaters summoned upon the Dark Lord’s return in Harry Potter and the Goblet of Fire. The elder Nott was one of the very early Death Eaters. Cantankerus Nott is widely believed to have authored the ‘Sacred Twenty-Eight’.
Ollivander – Makers of fine wands since 382 BC, the Ollivanders could make quite a claim to being among the oldest wizarding families.
Parkinson – An early girlfriend of Draco Malfoy, Pansy Parkinson was described as a ‘hard-faced’ Slytherin girl.
Prewett – Harry learned that brothers Gideon and Fabian Prewett (whose sister was Molly Weasley) ‘fought like heroes’ but were famously killed by Death Eaters in the First Wizarding War. Antonin Dolohov was convicted of their murder but it is said it took five Death Eaters to kill them.
Rosier – Evan Rosier was a Death Eater killed the year before Voldemort’s first downfall.
Rowle – Another Death Eater, Thorfinn Rowle was described as big and blond and got into trouble with Voldemort when Harry, Ron and Hermione escaped his clutches in central London in Harry Potter and the Deathly Hallows.
Selwyn – Dolores Umbridge claimed at one point to be related to the Selywn family, although whether this is true or not is unclear. A Death Eater named Selwyn was involved in the kidnap of Luna Lovegood, but his appearance in the Potter stories was brief.
Shacklebolt – Kingsley Shacklebolt was one of the wizarding world’s finest Aurors. Assigned to protect the Muggle Prime Minister during the Second Wizarding War, he was later named temporary Minister for Magic.
Shafiq – No appearances were made by the Shafiq family in the Potter stories.
Travers – One of the Death Eaters to escape from Azkaban, Travers was famous for helping murder the McKinnons.
Weasley – Bill, Charlie, Percy, Fred, George, Ron and Ginny were members of a strong dynasty which, despite suffering heavy casualties during the fight against He Who Must Not Be Named, is certain to continue for countless generations. Molly and Arthur had many grandchildren, including Ron and Hermione’s children, Rose and Hugo, and Harry and Ginny’s three – James, Albus and Lily.
Yaxley – The only Yaxley in the Potter books was another dastardly Death Eater.
Why didn’t the Potters make the Sacred Twenty-Eight?
Potter is a common Muggle surname. Harry’s family didn’t make the list, according to J.K. Rowling, because ‘the anonymous compiler of that supposedly definitive list of pure-bloods suspected that they had sprung from what he considered to be tainted blood’.