The theory that having multiple children of the same sex is a trait that ‘runs in the family’ has been debunked.

The University of Queensland conducted a study and proved that parents’ genes do not determine a child’s gender.

Dr Brendan Zietsch from UQ’s School of Psychology said the study was conducted a large range of subjects and pretty much proved that a child’s sex is random.

“We found individuals don’t have an innate tendency to have offspring of one or the other gender,” Dr Zietsch said.

“The chances are more like 51 to 49 of having a boy, but the genes of the mother and father don’t play any role.”

The study was undertaken from the Swedish population registers, going back to and including every Swede born since 1932, equating to more than 3.5 million individuals and their almost five million children.

‘’These findings have crucial implications for biological and evolutionary theories of offspring sex ratios,” Dr Zietsch said.


The research compared a person’s immediate family with the tests of whether a person’s child matched their sibling(s).

Dr Zietsch said a large amount of data disproves the theory around people having genes that could influence sex is wrong.

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