Those of us with older brothers tend to blame them for a lot of things: our low self esteem, an overly competitive nature, perhaps even a broken arm suffered in third grade.

Now it seems that younger siblings may have a genuine reason to feel hard done by having an older brother may reduce your chances of reproductive success.

Ian Rickard and colleagues at the University of Glasgow in Scotland collected data from 79 students and staff at their university with older siblings. They found that those born with at least one older brother were on average lighter at birth and also shorter in adulthood than those born with one or more older sisters. Rickard's team also analysed birth records from kept by the Lutheran Church in Finland for 653 women between 1709 and 1815 and found that the lifetime reproductive success of those born with an elder sister was 27% higher than for those with an elder brother.

By including families in which the older son died before their sibling was born the team was able to determine that reduced reproductive success was not a result of interaction between siblings but due to some other factor.

Rickard suggests that mothers who produce sons perhaps incurred a reproductive cost that could have consequences for future offspring.

"Male fetal testosterone may cross over to the mother and impact her immune function, compromising the weight of future fetuses," he says. "As birth weight and height are associated to health outcomes later in life, this could have potential implications to the long-term health of siblings."

Low birth weight has been linked to ovulation disruption, increased risk of depression and lower IQ. Because height is tied to attractiveness, there is some evidence that shorter men have fewer children. Having an older brother has even been linked with sexual preference.

"It is a very interesting paper," says Robin Dunbar, professor of evolutionary anthropology at the University of Oxford. "There do seem to be considerable knock-on effects of size, at least in males. Taller men earn more and are generally more successful in both social-political life and in the marital-reproductive stakes."