Glen Allsopp first came up with the brilliant idea for his business sat in his childhood bedroom at home in Newcastle, aged 16. Its rapid success led him to relocate from the UK to Cape Town before he even reached adulthood.

But where does such striking entrepreneurial spirit come from? Genes, parenting and education all likely play a role, but how does your family – especially your brothers and sisters – shape you?

Allsopp, the 30-year-old founder and CEO of detailed.com (an SEO consultancy that's worked with eight and nine-figure companies), is the youngest of three siblings, and he credits his position in the family with giving him the freedom to be creative and take risks.

“I could see my parents become more open to their kids doing different things as we all went from school and into the job market,” he says. “I had total freedom to quit my part-time job, leave college and essentially start a new life on a different continent.”

The idea that last-borns are more adventurous is just one of several theories swirling around the research literature on how our position in the family affects us in ways that play out in our adult careers. An even more popular idea – an almost taken-for-granted fact – is that first-born children, with their years of experience as top dog, are more disposed to become leaders.

Yet the scientific evidence for this is weak at best – some experts even describe the influence of birth order on personality as a “zombie theory”, i.e. one that refuses to die despite being refuted.

But that doesn’t mean our sibling relationships (or lack of them) have no impact. Recent findings suggest that instead it may be the age gap between siblings, the balance of boys and girls, and quality of the sibling relationships that matter more.

Those squabbles over who rides in the front of the car or who gets the latest bedtime may in fact be transformative. The battles and diplomacy of sibling life really can help equip us with the kinds of personal skills and attributes we’ll find useful as working adults.