Penelope answered: "Maybe they are not muggles, Mr. Weasley. I mean during a magical theory lesson, we have gone through the topic about squibs. Squibs are not active magic casters, but passive and Mr. Weasley, they have magical blood in their veins. What if my parents aren’t muggles, but squibs? I mean, what is the difference between a squib and a muggle?"