If you’re of a certain age, perhaps the most obvious group of siblings that offered up an interesting illustration of birth order was TV’s iconic Brady Bunch. Even watching it in re-runs as second- or third-generation viewers of the 1960s series, at least one member of the squeaky clean clan probably spoke to you as a kid in some way, shape or form … and it may have to do with where you personally fall in your own family’s age lineup.

Ever wonder why your oldest child agonizes over a book report while your youngest couldn’t care less whether he even finishes the book? It’s probably due, in large part, to birth order. Where you fall in your familial line influences your personality way more than you might think.

Firstborns

“Firstborns are the achievers,” says Dr. Kevin Leman, the best-selling author of The Firstborn Advantage (Baker Publishing Group, 2008) and The Birth Order Book: Why You Are The Way You Are (Time Group Books, 2011), among others, who has given countless interviews on the subject. “They’re our Presidents of the United States. They’re our astronauts in outer space. Of the first 23 astronauts, 21 were firstborns and the other two were only children. Firstborns are the architects or engineers, they’re English teachers, our dentists – anywhere where perfectionism pays off you’re going to find a proliferation of firstborn and only born children.”

But here’s the real kicker – it’s possible you could have more than one firstborn. “Huh?” you ask. There are actually variables that can upset the birth order, like if you place a lot of time in between your first and your second (such as five years) it’s almost akin to starting a new family … at least mentally. And gender can make a difference as well.

“I have five kids and I have one son in the middle of four girls. Is he the middle child? No, he’s the firstborn son,” says Leman. “He’s an executive producer of The Ellen DeGeneres Show. He does very well for himself. He’s not a middle child, he’s a firstborn. If there’s a five-year gap between the births of same sex children, you psychologically start another family.”

Leman also explains that without older siblings, firstborns and only children are just influenced by their parents, almost acting like little adults at an early age. They’re also more likely to have their nose in a book.

Middle Children

Interestingly, Leman says middle kids are the toughest to “pin down,” so to speak. They often play off of their older sibling and they’re excellent negotiators because since they never got their parents to themselves, they’re used to compromising on just about everything. For this reason you’ll find a lot of middle children drifting toward careers in the social sciences and similar fields.

“You wouldn’t be surprised to find a middle child who is doing very well in middle management because they’re relational by their nature and they negotiated for everything in life so they end up being pretty good negotiators,” says Leman.

Middle children also have the tendency to be fiercely loyal, but make no mistake, if you have two kids of the same gender right next to one another in birth order, it makes for some serious competition.

“It’s because we’re competitive by nature,” says Leman. “Two girls who are right next to each other or two boys who are right next to each other in birth order, if there’s a third or fourth child down there they’re going to find more of a chance to have a simpatico relationship by skipping a child so to speak because there’s not that head-to-head competition.”

Youngest

The baby of the family might feel like your most precious – the last one to go through every rite of passage so you’re feeling a bit sentimental as mom or dad. But for as cute and outgoing as they are, they may not be so conscientious or good with responsibility. They’re open to new experiences, but also a little too willing to take risks that could prove to be dangerous.

Still, Leman says don’t be afraid to parent your kids differently because they’re different people.

“Your firstborn should line up his toys or his DVDs or anything he’s playing with, you should see the perfection in his life already, whereas the second born (or youngest) could be walking around with his underwear in his back pocket,” he says. “He couldn’t care less. But here’s the thing, as a parent, you learn to treat the kids differently, so the kids don’t go to bed at the same time, put the little one down first, have different allowances – it’s the differences that make us a couple in relationships. Firstborn women are more likely to marry youngest males or middle males.”

Interestingly, because youngest borns are so social, they tend to excel in careers like marketing, where they can use their skills for the greater good.

It’s also important to keep in mind that the way in which we parent can be a variable in whether or not a child follows the personality traits typically associated with her place in the birth order. Leman notes a phenomenon he refers to as the critical-eyed parent, whose disappointment can have a huge impact on kids.

“That’s the parent who can spot a flaw with ease and they’re always ‘should-ing’ their kid,” he explains. “They’re pushing them and they’re essentially saying measure up. Lots of times, if that parent is strong enough, the firstborn child will do something very unusual. They’ll dig in, they’ll become a procrastinator and they won’t meet up to their expectations. They start a lot of projects and they’re good at the start but not at the finish, and they end up shooting themselves in the foot through life. If that happens then the second born, if they’re less than two years from the firstborn, might overtake the firstborn and become the leader of the pack.”

Wherever your children stack up in your family’s birth order, just remember one thing. Similarly to the people you meet out in the world each and every day, they have their positive qualities and less than flattering ones, but each is truly special in their own way and it’s our job as parents to help them flourish as such.

Kelly Bryant is associate editor of Boston Parents Paper.