"globally we average 1.07 boys to each girl at birth. Therefore most couples, likely including my aunt and uncle, were probably biased towards having boys."
> Most couples are biased towards boys over girls.
Yes, but the Bayesian argument shows that you can't infer that from your one sample. You only know that there is a bias towards boys because you have the global data that allows you to adjust the Bayesian prior to be peaked around the actual observed ratio instead of around 0.5. The Bayesian prior is still a much better prediction for any other case not yet observed than any value different from the prior that you might calculate from the data from just your aunt and uncle.
You have a point.
US statistics are 1.05 boys to each girl at birth. And that figure has been fairly stable for decades.
Which means that my point remains. Most couples are biased towards boys over girls.