Maybe think of it how our human babys grow, all 3 of my kids were with in an ounce of each other but they grow to be different sizes tall short ..... there DNA told them how to grow. With the sweet little pup in the picture will also grow to what there DNA tells them. So they may all be different sizes even if they all look the same size. Only pups we would think in grams not ounces. Hope that helps |