That child is the center of your universe and all children that come behind are then judged based on that first child.
Except for us - next, 19 months later we had TWO children and something was off. There were two of them, and they weren't at all like the first boy. We spent a lot of years buying in to the "they're just twins" crap until we had to realize that they were in fact different and not in a unique snowflake way.
I think we've adjusted, all of us, to the fact that like Marge Simpson says, they're our special little guys.
They asked us, when we were tested for autism "Do they express need?" and we mumbled stuff about how they would cry (at the age of four) or throw fits. But then they asked, "But do they point? Do they name things?" and we had to say no.
I was reminded this, when this past weekend going down the stairs with the girl as she is telling me "I want choc yolk (chocolate milk) and gogurt and breffass!"
This is normal. I don't know how we didn't see it for so long.