User blog comment:Brandie Janine Adams/Harry's Magical Blood/@comment-14.200.251.92-20120320084109

I just always thought purebloods had no known muggle ancestry. Therefore, any wizard or witch who has known muggle ancestry is half-blood or muggleborn (if no known wizard heritage at all). Therefore, Harry's children would be half-blood because their father has muggle ancestry. Only when a wizard's ancestry cannot be traced back to any muggle heritage can they be deemed pureblood. This is why many people faked their family trees in 1998. If they can fabricate that they have no muggle ancestry for at least two generations, they are deemed pureblood (but it's a broad and ambiguous term). For example, If someone's great grandfather was a well-known muggleborn and all the offspring have married purebloods and produced wizards, the person could not say that they were pureblood. The "grandparents" rule only applies figuratively and as an example.