Sibling birth order has zero effect on your personality. Yeah, right.

My baby brother towers above me. Twice as tall (well, almost). Feet double the size of my size six-ers. Hands probably bigger than my face. Shoulder-width almost double mine.

Quite clearly, he can protect himself better than my 163cm frame can protect him. But that doesn’t stop me trying.

That inherent urge to protect, lead, guide, keep safe. It may be a sibling thing. It may be because I’m older. I wonder if he feels it as strongly?

For decades, researchers have been intrigued about the personality nuances of children of different birth orders. (Particularly middle-children researchers – they’re particularly hung up on it, as middle children so often are… amiright?)

Are older children really more bossy, competitive, responsible, protective? (Not all of these things, surely?) Are younger children more reckless, more determined to prove themselves to be different, more manipulative, cheeky?

Or are these just stereotypes?

“Firstborns tend to be responsible, competitive and conventional, whereas laterborns have to ‘distinguish’ themselves and create a specific niche by being playful, cooperative, and especially, rebellious,” Belgian psychologists Vassilis Saroglou and Laure Fiasse wrote in a 2003 paper published in the journal Personality and Individual Differences.

A 2010 review of birth order literature also found that it’s common for middle children to be sociable, faithful in their relationships and good at relating to both older and younger people.

Tina Fey and Amy Poehler in "Sisters." Image Universal Pictures.

In 2009, a correlation between sibling order and spouse selection was discovered. It was found firstborns are more likely to be attracted to firstborns; middle siblings attracted to middle siblings; and youngest children attracted to younger children. If we're attracted to spouses of the same order - surely it's related to our personalities, right?


"The result is exactly what we should expect if birth order affects personality," psychologist Joshua K. Hartshorne, who was involved in the study, wrote for Scientific American. "Despite the adage that opposites attract, people tend to resemble their spouses in terms of personality. If spouses correlate on personality, and personality correlates with birth order, spouses should correlate on birth order."

Unfortunately though, it's not that straightforward.

As much as I'd love to blame every argument, and ALL the family tensions, on my "reckless", "manipulative", "cheeky" younger brother, more recent, large scale scientific studies do not back me up. (Rude, I know).

(Also, it's probably really, not his fault. He's pretty sweet. Only a little bit cheeky. I don't think he's responsible for ALL of the arguments. He definitely is responsible for most.)

Last year, two studies looking at almost 400,000 people overall, showed that huge disparities in personality types don't exist due to birth order. Firstborns were found to be more conscientious and less sociable than laterborns, but (against widely held misconceptions) they were also revealed to be more agreeable and less neurotic.

The nugget of these findings however, was this: That birth order explains less than one per cent of the variability between different people with regard to personality.

Less than one percent? See? I told you I wasn't that bossy.