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If you didn’t have any hooks, I’d say slim chance, around 5%. However, that legacy is pretty powerful, although I’m not sure how much it can carry you. I’ll guess you have around 20-25% chances, although maybe lower. If your family hasn’t donated lots of money to Harvard, it’s unlikely you’ll get in.
I’d say basically 0% chance given your GPA, and perfunctory extracurriculars. Legacy will only help you significantly if there’s money/donations involved.