Born in Munich, Lang had from a very young age been described as having a "weak constitution". Thus she was always struggling to keep up her education and performance while simultaneously maintaining her health. Once during a performance for the king and queen of Bavaria, Queen Caroline Augusta of Bavaria took notice of Josephine's poor state of health and arranged for her to go to Wildbad Kreuth in the German Alps to recover. During her stay there, she met Christian Reinhold Köstlin, a lawyer who also took to writing poetry on the side. According to all sources, the two fell in love and shared a happy marriage. Köstlin was a professor at the University of Tübingen.