I babysat fraternal twin boys and they had their own language with each other when they were little. It was adorable to watch them communicate. They are now in college and are still close. I have a friend who has an identical twin and she and her twin are as different as night and day, don't particularly like each other and live on opposite sides of the world. I am an only child, but even so my mother always compared me to the "ideal" she had in her head which I could never meet. I loved your comment that parenting requires an advanced degree. Very true!