A bright and spirited girl, 18-year-old Margaret chastised her spendthrift brother with the words: “Were I not a girl, I would be a soldier!” The following year she set out on the path towards that unlikely ambition when she exchanged her skirts for breeches and enrolled as a medical student at Edinburgh, shrewdly reducing her age to explain her hairless chin and petite frame.
Barry was the second child born to Jeremiah and Mary-Ann Bulkley, and was given the name Margaret Anne. . . . A third child appeared in the Bulkley family and was named Juliana. Although presented as being Barry’s sister, it is likely that she was Barry’s daughter as a result of childhood sexual assault, as the charwoman who discovered Barry’s sex when laying out the body stated that pregnancy stretch marks were present.
Source: https://en.wikipedia.org/wiki/James_Barry_(surgeon)