Does birth order influence our relationships?

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I’m first-born. My husband is too. I’ve had relationships with men who weren’t number one kid, and they didn’t go so well. Was the different order of birth a decisive factor in that negative outcome? Or did it play a part, at least? And if that was the case, is there anything that can be done to overcome this uncontrollable bias?

I’m about to bring you the results from a new study commissioned by dating website Plenty Of Fish. The group sought information from 7.6 million singles in the US and Canada, and, upon exploration of the data set, decided those born first stand a better chance of landing a loving, long-term relationship than their siblings. Only children were also less lucky in love.

That sounds like good news for me, bad news for everyone not in my shoes. It also sounds trite - considering the vast ‘other’ category would have significant profit potential for a business based on partnering potential. Is there any truth to the matter?

Studies have shown birth order plays a significant role in shaping our character. Some describe it as the result of the Darwinian struggle for survival from the moment we’re born. Others suggest we can’t help but grow into preconceived notions of our familial ‘roles’; first-borns are supposed to lead their siblings, middle children are supposed to play peacemaker, and the baby is meant to be adored by everyone, yet never taken seriously. Only children are supposedly lonely, or resourceful at best.

A study, authored by evolutionary psychologist Dr Catherine Salmon, was published in the journal Human Nature in 2003. From surveying 245 undergraduate university students, Salmon found those who were ‘middleborn’ gravitated more towards people outside their family group than within. They expressed more positive views towards friends than their family, and they were less inclined to help family in times of need.

This is interesting enough, but when she explored mating strategies, she found that these also appeared to be influenced by birth order, most notably in the area of infidelity. Her research found middleborns were the least likely to cheat on a sexual partner: 80 per cent said they never strayed, compared with 65 per cent of firstborns, and 53 per cent of lastborns. So does that mean good marriages are more likely for those born between two siblings?

But we all know household arrangements are hardly routine. There are adoptive families, foster families, blended families, separated families, estranged families. Families who have secret members, families who have disabled members, families who comprise just one; an orphan.

This has always been the case, but there’s a greater awareness and acceptance of diversity today. Does that impact the influence of birth order? Certainly, an older child raised as an only child may not fit the ‘first-born’ mould. And what about gender - is that a mitigating factor? I know middle children who are also the only female child in the brood; their personality traits may be more like those of an only child than a middle because they're so different from the others. So how do you figure that one out, science?

“I know myself I’ve only had successful relationships with people who were the youngest children,” one of my mates says. “My previous relationship was with a first-born. They were too bossy, too demanding, and too easily exasperated. In some ways, we fell into an annoying pattern where I’d expect him to take charge, and he’d expect me to be the baby. I don’t know if it was just our personalities being mismatched, or whether our birth order really did impact our personalities to the extent we were never going to be happy, or whether it actually had nothing to do with it.

“But the stats, I suppose, speak for themselves. I’m happily married now, and we're both the youngest kids.”

It’s extraordinary to think in this age of self-direction and independent governance something as pivotal as our personal relationships could be governed by circumstances so beyond our control. With so much of it all up to chance, is there any point in worrying about those influential factors beyond our control? Of course not. There’s a point to being conscious of, but not hung up on, all those seemingly insurmountable things - if only to find solace in the fact that when it comes to achieving love and sex success, the best thing you can do is but try.

Katherine Feeney is a journalist with the Nine Network Australia.