There are many songs about Handsome Cabin Boys and female Drummers on the folk scene and there were probably plenty of real examples of these in real life. Dr James Barry rose to the rank of Inspector-General of the British army medical corps at the time of the Crimean War. It was only after his death that "he" was found to be female, and also showed signs of having given birth to a child. Strangely, she greatly disapproved of Florence Nightingale bringing nurses to the army hospitals. See THIS SITE.

There is also the legend of the Pope who proved to be female and was lynched when she gave birth in public. A lot of the stories claim she was British.