Despite the paucity of empirical evidence from Bruni, there is a large body of research on siblings. Having a sister makes boys kinder. Having a brother makes girls better at figuring out spatial problems. Having an older brother raises the odds of a man being gay. Siblings duke it out more over toys and possessions than anything else (big suprise). And then there's the occasional nugget like this:
A new study of Bolivian villagers shows a link between having a younger brother and slightly increased blood pressure levels later on in adulthood, though Brandeis University researchers did note the effect seemed to diminish with age. Huffington PostPhew, have always wondered about blood pressure in Bolivian villagers. I would have brought you more curious sibling studies but every single article started with the author's attention-hogging little brother or freakishly talented older sister, daughter, son or other personal details that kept me from the data.
Anywhoooo, there is no talking siblings without an appearance by that darling of the media and the public imagination - birth order. I can't possibly get into that labyrinth of mythical and valid results. But just as first-born/last-born gets a nod the discussion then must turn to the only child...optimal number of children....parental happiness...adopted parents....step parents...co-habitating unmarried parents.....co-habitating unmarried step-parents.....gay parents.....blah blah blah.
Are sibling the most critical predictor of success, happiness and future mental health? That question is beyond the scope of this post but I can tell you one thing for sure. Everybody has an opinion and they're likely to give it in the opening paragraphs of their news story or blog post along with a personal anecdote about their own brother, sister, daughter, son, great aunt or neighbor. Everyone's an expert. Everyone's got a story. Why call on science when we have our stories.