Many things that are called nuts actually aren't by the strict botanical definition. For example: almonds, Brazil nuts, cashews, macadamias, peanuts, pecans, pine nuts, pistachios and walnuts are all...
Not in Grape Nut Flakes, but I'm not too sure about actual Grape Nuts. I would go to the store and check the ingredients on the nutrition label on the side of the box. That would probably tell you.