According to new research your older brother or sister really is smarter than you.
The new Dutch study shows that birth order affects intelligence, making the first-born the smartest, while a long list of other studies link personality, weight gain and even premature death to where you're positioned in the family lineage.
Here are some of the theories linked to birth order:
A number of studies have been conducted that suggest IQ scores decline according to birth order. Why this is the case still isn't clear, but a popular theory is that the extra one-on-one time, attention and patience parents give their first-borns, compared to children arriving later, gives them a intellectual head start.
A study from the University of California suggests first-borns are the achievers, more dominant, religious, conscientious and neurotic. They also earn more, are more responsible, anxious and organised, and they tend to stick to the rules.
Middle-borns on the other hand are rebellious, impulsive and open to new experiences. They perform more poorly academically and often procrastinate, but they are also the peacemakers.
And the lucky last-borns are the family favourite they're often the joker, are warm, sociable, extrovert and creative. They are also the most likely to question authority.
Later-borns are more likely to die prematurely. One possible explanation is that later-borns are also the bigger risk takers and that their adventurousness may at times put them in harm's way.
Eczema and asthma
Research shows that later-borns have a reduced risk of suffering from common childhood illnesses like eczema and asthma. One theory is that younger children are exposed to a wider range of infections by their older siblings and therefore have strengthened immune systems.
Later-borns often have more sexual partners than first-borns. According to researchers, this finding suggests first-borns are more interested in finding a long-term mate, which is a reflection of the fact that they want to uphold the values of their parents, while the later-borns are more rebellious.
Later-borns are less likely to be overweight. It's not clear why this is, but one theory is that over-protection and over-feeding of the first-born may lead to obesity.