At least some content in this article is derived from information featured in Harry Potter: Hogwarts Mystery. Spoilers will be present within the article.
The Sacred Twenty-Eight were, according to the author of the Pure-Blood Directory (widely believed to have been Cantankerus Nott), the twenty-eight British families that were still "truly pure-blood" by the 1930s.
The Sacred Twenty-Eight comprised the families of:
Notes about the Sacred Twenty-Eight
Interestingly, the Ollivander family is considered one of the Sacred Twenty-Eight, despite Garrick Ollivander's mother being Muggle-born prior to the book's publication. It is possible, however, that the Directory's author was unaware of or overlooked this for other reasons.
The Potter family was excluded from the list because it was also a common Muggle surname, and that Henry Potter also took an outspoken pro-Muggle view during his time in the Wizengamot. This was despite Dorea Black marrying Charlus Potter, and not being disowned, which would almost certainly indicate that the family had no known Muggle ancestors or relatives. Also, James Potter was a pure-blood. One possible theory indicates that the author of the Directory considered the Potters and other "pure-blood" families (such as the Princes, the Crabbes, or the Goyles) to have some amount of Muggle ancestry.
Some families (most famously the Weasley family) spoke out against the list in spite of their inclusion, declaring that they certainly had muggle ancestry and were not ashamed of it. The families who were proud of being included or who wished they had been labelled them "blood traitors" in retaliation.
Although the Malfoys were noted as respectable members as one of the Sacred Twenty-Eight (a title they are proud of), they did not take the pure-blood supremacy to the point of inbreeding: they were willing to marry half-bloods, many of whom are shown in their family tree. As they had no Muggles or Muggle-borns in their family tree, they were still a pure-blood family, just not as fanatic as the Blacks, Gaunts, and Lestranges, whose members do not marry half-bloods, Muggles, or Muggle-borns.
- Pottermore (First mentioned)
- Wizarding World (Mentioned only)
- Harry Potter: Hogwarts Mystery (Mentioned only)