What do you think the Shacklebolt family are like as members of the sacred 28? Are they usually purists whose ways Kingsley unlearned over the years or are they overall more neutral like the Longbottoms? Perhaps he is part of a half-blood branch like Hannah Abbott?
When it comes to the Sacred Twenty-Eight, I believe that a lot of the in-universe discrepancies on the list can be explained away by saying that the author was actually naming a series of Houses that held similar anti-Grindelwald sentiments as he did, and that it actually had very little to do with who was ātrulyā pureblood and who was not. As a result, while I believe that the Shacklebolts are an old wizarding family and that Kingsley himself is a pureblood (and also a Slytherin!), the family as a whole is more similar to the Abbots in regards to its stance on intermarriage with muggleborns and half-bloods.


















