Caused

It would be hard to believe that Juliette Nadia Boulanger, the most influential musical pedagogue of the twentieth century, was not always an enthusiastic student of music. In fact, even in 1892, when little Nadia was five years old, she would cry and hide upon hearing music from the salon — a rather humorous situation, as her father, Ernest Boulanger, was a well-respected composer, conductor, and professor of singing at the Conservatoire de Paris. But a remarkable development came late that year, when her mother Raïssa conceived another child. Throughout her mother's pregnancy, Nadia paid much greater attention to her father's singing lessons and began her study of the rudiments of music. 

And in 1893, she became the older sister of Marie-Juliette Olga Boulanger, known as Lili. In her later years, Nadia would say that Lili's birth marked the moment she became an adult. Before she saw her sister for the first time, Ernest asked for her solemn promise that she would make herself responsible for the baby's welfare.