When Roland Simpson considers the different personalities of his three boys, Harry, Alexander and Owen, he can't detect many first-born, middle child or "baby of the family" traits.
"The birth order hasn't made much difference to their personalities," Mr Simpson said.
"If anything, it's the way my wife and I have parented."
It is widely assumed that first-borns are driven, responsible, and neurotic. Children born later are thought to be more indulged, sociable, and adventurous.
But these stereotypes have been smashed by two large international studies which examined whether birth order determines enduring personality traits.
"People who define themselves in these terms are making a mistake," University of Melbourne psychology Professor Nick Haslam said. "Birth order doesn't determine your personality at all."
German researchers who analysed 20,000 people from Britain, the United States and Germany found a person's position among their siblings had no bearing on their imagination, extroversion, conscientiousness, emotional stability or agreeableness.
"Birth order does not have a meaningful and lasting effect on broad personality traits," the researchers concluded in a paper published in the Proceedings of the National Academy of Science this week. "The development of personality is less determined by the role within the family of origin than previously thought."
Researchers said that some of the personality traits linked to first-borns often simply reflected their greater maturity as the eldest child.
These findings echoed those of American researchers who analysed 400,000 US high school students. Both studies controlled for age, sex and family size.
Professor Haslam said that while birth order could play a part in family dynamics when children were growing up, it had no bearing on what you were like as an adult.
"These things may describe your role in the family context, but when you're an adult, you're no longer in that context," Professor Haslam said.
Perceived personality effects of birth order are often linked to changes in parenting style as more children are born.
"With your first-born, you're on top of things. Gradually your house is reduced to chaos, you're not as strict enforcing bedtimes, homework, routines," Professor Haslam said. "The result of not as rigidly parenting is a less rigid child."
He warned that while birth order stereotypes had their genesis in families' real experiences of childhood, viewing children through the lens of birth order could actually cause resentment among siblings in adulthood.
However, birth order has been proven to have a slight effect on intelligence and physical health. First-borns tend to be smarter, have better cardiovascular health and are less likely to die prematurely, than their siblings.
Each later-born child has an IQ one point lower than the sibling above them. Professor Haslam said this could be due to the fact that subsequent children do not benefit from the singular parental attention the eldest child receives.
First-borns also teach their siblings, which boosts their own learning. Meanwhile, more children in the household diminishes the overall calibre of the intellectual environment as children outnumber adults.
Mr Simpson doesn't think the order in which his three boys were born has had much impact on their personality, and believes the way he and his wife have parented has had more influence.
"With your first child you're still learning, you've got your L plates on. The youngest tends to fend for himself."
On the cusp of adolescence, 13-year-old Harry is the most inwardly focused, and into computer games.
Middle child Alexander, aged 12, is the social one, Mr Simson says. "He's almost like a member of the United Nations, he acts as a mediator between the other two."
Youngest son Owen, aged nine, is an extrovert. "He does dancing, he likes to be on stage ... he'll talk to anybody about anything."
