siblings: more in common with strangers?

i found this recent article freeing: http://www.npr.org/2010/11/18/131424595/siblings-share-genes-but-rarely-personalities

it's about a study that showed that while siblings tend to share many physical characteristics and cognitive abilities due to genetic similarities, when it comes to personality, they are more different than anything else. here are a couple short excerpts:

--------------
Then in the 1980s, a researcher named Robert Plomin published a surprising paper in which he reviewed the three main ways psychologists had studied siblings: physical characteristics, intelligence and personality. According to Plomin, in two of these areas, siblings were really quite similar.

Physically, siblings tended to differ somewhat, but they were a lot more similar on average when compared to children picked at random from the population. That's also true of cognitive abilities.

"The surprise," says Plomin, "is when you turn to personality."

Turns out that on tests that measure personality — stuff like how extroverted you are, how conscientious — siblings are practically like strangers.

"Children in the same family are more similar than children taken at random from the population," Plomin says, "but not much more."
In fact, in terms of personality, we are similar to our siblings only about 20 percent of the time. Given the fact that we share genes, homes, routines and parents, this makes no sense. What makes children in the same family so different?
-----------------------------
the article goes on to set up 3 different theories about why growing up in a shared environment actually causes siblings to be *different* rather than alike. if you are a geek like me, read it--it's fascinating to think about. best part of the whole thing is the last line:

"So, this Thursday as you eat your turkey, look across the table. There, you may see a brother, a sister, a step-sibling, a twin. And maybe they're your friend, and maybe they're your enemy, but one thing is for certain: Their very existence has had a profound influence on your life."


this gave me some peace, given that my general wellbeing from day to day seems to depend wholly on sibling dynamics. it was a gentle reminder that my kids will be different like night and day, and no one can expect distinct individuals that spend 90% of their time together to get along well all the time. it also shed some light and forgiveness on my relationship with my brother, and mike's with his brother. i like science.