Is MY an only child?

Not to turn this in to a mirror of everything Matthew Yglesias writes, but I think the answer to this question:

Say you knew two families with kids applying to college. One kid gets a 1028 on his SAT and the other kid gets a 1021. Are you really going to say something dramatically different to the parents of Kid B?

is that it's precisely the smallest differences among and between families which get magnified and blown out of proportion.

As a personal example, my twin brother emerged from my mother a whopping six minutes after I did. There's no particular reason for this, obviously. I'm not six minutes "older" than him in any real sense. Nevertheless, my brother had to endure years (and may still have to endure, I don't see him frequently) being called the "younger brother", which, in his case, is pretty patronizing.

Now there are obvious differences between my example and Matthew's, but based on my experience, I can absolutely see Kid A being treated differently - even dramatically different - than Kid B. Even better, I bet the parents of those respective, hypothetical children could get very acrimonious. Parents A will bring up their kid's extra 7 points at every opportunity - because they're rightly proud, not trying to be jerks - and Parents B will quietly seethe.