Bacchus MindEconomy Chronicle

By all accounts, my brother and I have both built good careers- his in a dynamic, creative field; mine in a more analytical and structured world. We were raised in the same household, by the same parents, with the same expectations around hard work and integrity. Yet in life, we’ve always danced to different rhythms, even whilst under the same roof.

He’s imaginative and expressive- an idea generator, someone who’s always staunchly followed his dreams. I’m the planner, the realist, the one who makes lists and colour-codes calendars. While we both work hard (a non-negotiable family trait), I know that much of my ambition was quietly modelled off watching him. My older brother, as the first-born, was always the trailblazer.  I, the youngest, often found myself pushing just a bit harder- not to compete, but to keep up with someone I deeply admired.

As it turns out, we’re part of a much bigger story. One that psychologists and economists have been studying for decades: the psychology of birth order—and how it subtly shapes who we are, how we behave, and even how we build our lives.

Birth Order Isn’t Destiny- But It’s Definitely a Force

Alfred Adler, one of the leading early 20th-century psychologists, was among the first to suggest that birth order affects personality development. First-borns, he proposed, are often responsible, protective, and achievement oriented. Middle children become adaptable negotiators. Last-borns (such as myself) are expressive, social, and frequently challenge convention.

Modern research both supports and complicates this view. A major study published in PNAS (Rohrer et al., 2015), drawing on data from over 20,000 individuals across the US, UK, and Germany, found modest but measurable differences in personality traits by birth order. First-borns scored higher on conscientiousness and leadership. Later-borns leaned more toward traits like openness and sociability.

The beauty is in the nuance.

You see it in things like how we speak in meetings—first-borns often wait their turn, structured in their delivery. Younger siblings? We’re more likely to jump in mid-conversation, driven by a lifelong muscle memory of trying to be heard over older, more articulate siblings. (I’m guilty. I interrupt. A lot.)

It is visible in career paths too. My brother (the first-born) is the big-picture thinker. He takes calculated risks, but always with a grounded sense of duty. I, the younger one, approach decisions with precision. I analyse. I spreadsheet. Perhaps because I watched him figure life out first, I made fewer early mistakes- but I also took fewer early leaps.

Parental Investment, Sibling Shadows, and Family Roles

Economists have examined how these patterns manifest not just in personality, but in life outcomes. A study by Black, Devereux, and Salvanes (NBER, 2017) using Norwegian registry data found that first-borns tend to earn more on average—around 2–4% over their lifetimes—even when accounting for factors like family income and education. One explanation? First-borns often receive more parental attention and pressure in early years- a concept known as the resource dilution hypothesis.

In our house, my brother bore the brunt of the “you must set an example” mantra. He got the tighter curfews, the stricter homework checks, the higher expectations. By the time I came along, my parents had relaxed (just slightly) and as a result, I enjoyed somewhat more flexibility. However I also had a front-row seat to his efforts: his late nights, his discipline, his willingness to push himself. That shaped me in ways I’m only now beginning to appreciate.

While first-borns may appear to dominate in structure and salary, younger siblings have their own set of internalised advantages – that have a tendency to show up in creativity, adaptability, and yes, sometimes even charm.

A 2016 study out of the University of Birmingham found that later-borns are more likely to become entrepreneurs, suggesting that traits like risk tolerance and nonconformity may come more naturally to them. That aligns with broader research on birth order and personality- later-borns often report being more open to new experiences, more socially attuned, and more inclined to challenge norms.

Inherently, it makes sense. As the younger sibling, you’re born into someone else’s world. To stand out, you adapt. You learn to be louder, funnier, more flexible. You become a shape-shifter in social situations- and in work environments, that can be a major asset.

How Sibling Sequence Shapes Romantic Compatibility

One of the more charming areas where birth order psychology finds real-world application? Romantic relationships. Numerous psychological studies have found that opposites (at least in birth order) often attract. According to family psychologist Dr. Kevin Leman, author of The Birth Order Book, the most stable pairings are often those where each partner brings complementary traits to the relationship. In particular:

• First-borns tend to pair well with youngest children because their roles align in an almost intuitive way: one leads and plans, the other brings playfulness and emotional spontaneity.
• Meanwhile, two first-borns may struggle over control; two youngest children may lack grounding.

This dynamic plays out beautifully in my own marriage. I, the youngest sister followed a familiar trope – I married a protective older brother- a classic first-born. He is methodical, calm, quietly authoritative. I, on the other hand, bring lightness to the mix. I challenge his assumptions, push for spontaneity, and (as youngest siblings often do) make space for the emotional undercurrents. Whilst we may joke about our respective inherent roles, they’ve helped create balance. He helps me slow down. I remind him to let go. Our dynamic, built on mutual respect, also echoes the subtle gravitational pull of our childhood places in the world- me following the example of an older brother I admired, him looking out for someone younger with natural protectiveness.

There’s something poetic about marrying (or simply building a life together) with someone who mirrors your sibling dynamic in a new, more intentional form. We are not reenacting our childhoods- but we’re not starting from scratch either. We’re building on something already understood at a deeply fundamental level.

What This Means for Families: Balance, Belonging, and Unspoken Scripts

Understanding how birth order influences personality and behaviour isn’t just an abstract curiosity—it has real-world value for families navigating sibling dynamics, parenting strategies, and lifelong relationships.

Within families, birth order often sets the tone for unspoken roles:

• First-borns are frequently cast as the responsible ones—the helpers, the achievers.
• Middle children become bridge-builders.
• Youngest siblings lean into humour, flexibility, and often rebellion.

These roles crystallize early and can persist into adulthood. My brother was the gold standard in our family. While our parents didn’t explicitly treat us differently, the invisible scripts of who we were “supposed” to be sometimes played out regardless. Being aware of these dynamics allows families to redistribute responsibilities and affirm each child for who they are- not just who they are in relation to their siblings.

For me, there was great freedom in realising that I didn’t have to be “the opposite” of my brother to define myself- I could admire him, follow his lead in some areas, and still forge my own path.

This awareness also strengthens adult sibling bonds. Understanding that my occasional interrupting is part of a younger sibling script- and that his planning instinct stems from years of being the “responsible one”- allows us to meet each other with humour and compassion. Ultimately, birth order shouldn’t box anyone in. It can be a beautiful and insightful lens- one that helps families grow in empathy, appreciation, and understanding of the subtle ways our early roles ripple through the rest of our lives.

Birth order may shape us, but it doesn’t limit us. If anything, it deepens the stories we carry.

In the End, It’s All Love (and a Bit of Science)

My brother will probably laugh reading this. He’d say I’m overanalysing as usual. Perhaps I am- but that would negate the entire point of this blog post I suppose. Regardless I’ve come to see that our birth order didn’t just influence who we are individually- it shaped our bond.

He was my built-in mentor, my example of how to work hard, how to care deeply, and how to keep your feet on the ground even when you’re dreaming big. I was the one who asked too many questions, made too many charts, and maybe talked over him at the dinner table (sorry, again).

And now, married to another oldest child (kind, patient, wise in his quiet way) I see how much those early roles still echo. They don’t define us, but they do give us a kind of emotional shorthand. Between us all (siblings, spouses, and of course, ourselves) we’ve built something strong. Something shaped by birth order, yes, but also by love, laughter, and the unspoken choreography of growing up, side by side.

Even when you’re interrupting.

References & Further Reading

• Rohrer, J. M., Egloff, B., & Schmukle, S. C. (2015). Examining the effects of birth order on personality. PNAS, 112(46), 14224–14229.
• Black, S. E., Devereux, P. J., & Salvanes, K. G. (2017). Birth Order and the Earnings of Young Men. NBER Working Paper No. 13224.
• University of Birmingham (2016). Sibling Order and Entrepreneurial Tendencies.
• Sulloway, F. J. (1996). Born to Rebel: Birth Order, Family Dynamics, and Creative Lives.
• Salmon, C., & Daly, M. (1998). Birth order and familial sentiment: Middleborns are different. Psychological Science, 9(5), 355–359.
• University of Birmingham (2016). Sibling Order and Entrepreneurial Tendencies.
• Leman, K. (2009). The Birth Order Book: Why You Are the Way You Are.