Here are a few differences I have noticed in having three children vs two:
1. You need two shopping carts at the grocery store. One for the kids and one for the food.
2. Someone is always crying or whining about something or someone, which means there is never a quiet moment in the house.
3. A king size bed isn't as big as it appears.
4. Having close "family friendly" friends is essential.
5. In the exact moment you sit down, someone (a kid, a spouse, a cat) is going to need something, and it is going to be "an emergency."
I have a sign that hangs in my kitchen that reads "Faith, Family and Friends." I am finding more and more that I rely heavily on all three of these aspects of life. I just wish there was a word that started with F that meant wine... because, to me, it ranks right up there with the other three.