“When Robert was a little over two years old, his mother gave birth to a girl, the first born to her, but still she showed great interest in Robert; talked much of his future and took great interest in teaching him to live according to the Bible.”
That was the only sentence in the book that Gann ever mentioned about his sister, and his sister never appeared in the story again.
While it may seem like a trivial fact in the story, it is believed that Gann actually hid some important information in it.
Hint: look at the astrological chart slightly after Robert’s birthday in 1908. Robert was born in 9th June, 1906.