From "A Little Society", by Casey N. Cep, boldface mine:
Despite Charlotte Brontë’s insistence that her sister Emily wrote Wuthering Heights, the rumor that their brother Branwell penned the novel has persisted. ...The persistence of the rumor reflects the curious, cloistered upbringing of the Brontës, but also the more universal experience of siblings. Collaboration and competition between brothers and sisters exists no matter their vocations, but literary siblings challenge our assumptions of lonely genius, isolated writers alone at their desks. Patrick Brontë, father to the four artists, who raised them himself after their mother died, wrote: “As they had few opportunities of being in learned and polished society, in their retired country situation, they formed a little society amongst themselves—with which they seem’d content and happy.”“A little society” is the perfect description of siblings. Brothers and sisters have long encouraged one another’s literary careers: letters and drafts change hands; carefully chosen words of praise and criticism pass between lips; scraps of paper, coveted notebooks, and particular pens move between writing desks.