Are you saying that children's sex is heritable? I don't think there is any strong evidence for that (just weak evidence of tiny effects). Or are you just saying that for any 50/50 distribution, there will be some outliers that seem surprising, but are explained by simple statistics?
There are genetic and biological predispositions at the individual level that make some couples more likely to have one or the other gender children. So it is not at all surprising and there are many examples of parents having all boys or all girls, it does not mean they are selectively aborting to achieve a goal.
