How are Harry Potter's children halfbloods?

I would guess it's because Lily is a muggle-born.

Lmao that's not how genetics work. If someone is half black/half white and has a baby with a 100% white person, that baby is then 75% white and 25% black.

So really, Harry's kids should be quarterbloods.

Lily a muggleborn.

Actually, Harry and Ginny's children would be classed as purebloods, not halfbloods. It's all down to the grandparents:
4 Muggle grandparents makes someone a Muggleborn (so the child of 2 Muggleborns would also count as Muggleborn).
1, 2 or 3 magical grandparents makes someone a halfblood.
All magical grandparents makes someone a pureblood.

Lily, James, Arthur and Molly were all witches and wizards, so the 3 kids would be classed as purebloods.

However, I guess there'd be some extreme pureblood manic wizards and witches who'd say any known Muggle ancestors, no matter how long ago, would make someone halfblood only.

In Harry Potter, half-blood is a term used to describe anyone who is between being a muggleborn and pureblood. It doesn't matter if the child is exactly 50/50 or if the ratio is more 25/75, like in Ginny and Harry's case. They're still half-bloods.

Well think of it like this, there's muggle-borns and pureblood, everything in between are half-bloods. You could be a real half-and-half, half-blood, like Harry, as he had a muggle-born and a pureblood for parents, you could also have a muggle and a pureblood as parents and still be a half-blood. Since the wizarding world has existed for a long time its doubtful that there's anyone who's an actual half-and-half, half-blood, due to the fact that real pure-bloods don't really exist anymore (sorry Draco but it's true). So what I'm trying to say I guess, is that if you're not a pure-blood and not a muggle-born then you're half-blood. Sorry if this answer was a mess lol

Because maybe since Harry is Half-Blood, his kids became Half-Blood as well but Ginny is Pure-Blood so technically James, Albus and Lily should be Pure-Blood.

Harry and Ginny are both wizards so when they had kids they are all pure blood only if Harry married a muggle his kids would be half bloods but he married Ginny!😌