User blog comment:IvyBushe/Muggle-born parents and their children./@comment-2226001-20130417004459

If you are born to two Pure-bloods, you are Pure-Blood.

If you are born to two Muggles, you are Muggle-Born.

Everyone else (save for Muggles, Half-Breeds, and Squibs) are Half-Blood. This is true whether you are born to two Half-Bloods; a Half-Blood and a Muggle; a Half-Blood and a Muggle-Born; a Half-Blood and a Pure-Blood.