There is no hard and fast rules for how much you need to plant to feed a family of four (or six or ten), but there are some general guidelines based on plant output. We are a family of 7, with only 6 veggie eaters.
Many websites give general ideas of how much you should plant, but this chart from About.com is by far the best one I’ve seen. It focuses on common vegetables that most people use, rather than pulling in every odd variety under the sun. Because it’s limited in scope, you can extrapolate how much broccoli you would need to plant if you favor that over cauliflower.
Keep this handy and reference it when you’re planning your garden. I almost ended up with 10 times the number of peas I would need in my plan, because I didn’t realize how much they grow in such a small area.