That's not true, the Dursleys were just horrible people to Harry because Petunia was so against wizards. God, read the f-ing books people<---well props to them for coming up with an interesting theory even if it isn't right
Thing is, Petunia had Muggle parents, so if she was magical she would have been Muggle-born. A squib is a pure-blood who can't do magic. That said, I love the idea of Petunia having magic but unwilling to own up to it!
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