There is only so much protein your body can absorb (with slight variances to account for age, height, and weight) and the rest is just discharged. Meat is only one source of protein, but can also be another source of important nutrients (like iron). So, a person doesn't need much more than the 'deck of cards' serving size at any given meal.
That said, meat can taste awfully good, and sometimes a larger portion might even be appropriate if you are trying to get in a higher number of calories.
I often eat a smaller portion of protein, but my 6ft 4in athletic sons eat A LOT of food, and their meat serving is proportionate to the servings of other foods-- carbs, fruit, and veg. We also mix up our sources of protein--chicken, pork, lamb, fish, cheese, legumes, eggs.
For what it's worth, I use a pound of ground beef when I make spaghetti sauce, but I use an equal amount by volume of finely chopped veg ( carrot, celery, onion) and this feeds 4 adults ( the boys are in their 20's) -- so, much like you and your family do. However, I've also seen youngest son eat a steak almost the size of his dinner plate...and don't get me started on what eldest eats after a triathlon!
