The debate whether firstborns really have advantages over their younger siblings has been examined in a new study.
Researchers first examined the status of firstborns among Washington power brokers in 1972.
"I expected that there would be a disproportionately high number of firstborns among members of Congress. "And that's exactly what I found," the National Public Radio quoted psychologist Richard Zweigenhaft of Guilford College, as saying.
Out of 121 representatives and senators included in his sample, Zweigenhaft found that 51 were firstborns, 39 were middle children, and 31 were youngest children.
From corporate CEOs to college professors to U.S. presidents and Supreme Court justices, firstborns do edge out later-borns. There's even evidence that firstborn children are about 3 IQ points smarter than their second-born siblings.
"When the second [child] comes along, the oldest still gets half of all that [attention], so younger siblings never have a chance to catch up," said Frank Sulloway, a visiting scholar at the Institute of Personality and Social Research at the University of California, Berkeley.
Parents don't mean to act differently towards their children - partly it's the inexperience that makes some first-time parents go overboard.
Experts say it's never entirely predictable how birth order may influence our personalities, behaviours or family dynamics - there are plenty of firstborns who don't fit the mould.
"I'm not sure I would say that birth order plays a strong role in who we become. Birth order contributes to who we become," said Zweigenhaft.
After all, we're all amalgams of many childhood influences, from teachers and peers to random life events, including turns of good luck and bad.