Not to be confused with Purebloods.
Royal Purebloods are Draconians that were born into the royal family, and are made to inherit the throne. Purebloods are the children of the current rulers that have married another person of royalty. This means that the child has 100% of the royal bloodline in them, and was not born with only half the blood of a royal. Half-breeds are usually not allowed to inherit the throne, but there have been exceptions.