The diapers. An unbelievable amount of diapers. We have two diaper pails and I empty them daily, but I still swear my house smells like urine.
Boogers and snot. An unbelievable amount of boogers and snot. A little less now that I've given up dairy, but still. Kleenex called to personally thank me for my patronage. (Not really, but they should).
Laundry. An unbelievable amount of laundry. The two of them combined weigh a total of 36lbs, and somehow, I still end doing a load every single day just to maintain. Someone needs to invent the Roomba for laundry folding.
They get hiccups at the same time. All the time.
Your oldest will all of a sudden use the words "My" and "Mine" on the regular. My Blanket! My Bottle! My mommy! My July 2013 copy of Runner's World Magazine! in response to their little sibling showing an infant-sized amount of attention to something or someone.
When one cries for more than 2 minutes, the other is going to start crying even harder. Especially in the car, when they know you can't escape.
There is no such thing as telling the older one: "We have to be quiet, sissy is sleeping." That is apparently code for PLEASE TALK LOUDER SO THAT SISSY WAKES UP!
You have to maximize every single minute of every day in order to stay sane.
That overwhelming fear you had when you were pregnant that your heart doesn't have enough room to love two children equally? You finally realize it's total nonsense. Not only has your heart grown to a size you didn't know existed, but now you get to look at both of your children sitting together and realize that your entire world is complete. Because you could never have imagined a love this great, and you know nothing you could ever accomplish in this life could be more astonishing than these two precious miracles.
You look at your life daily and realize you wouldn't trade it for anything in the world.