Most developed country have made great progress toward a better equality between men and women even if it's not yet perfect. Throughout history, some societies where more equal than others and some where even matriarchal societies.
I'm wondering what factors either form real world or invented but plausible would contribute to shape a more equal society between men and women in a fictional world? Put aside birth control.
Regarding genders, I will limit the scope to men and women for this question.
At conception we all start life as equals, but at birth we are immediately treated differently based on whether we are a boy or a girl. The Universal Declaration of Human Rights acknowledges that men and women are not the same but insists on their right to be equal before the law and treated without discrimination. Gender equality is not a ‘women's issue' but refers to the equal rights, responsibilities and opportunities of women and men, girls and boys, and should concern and fully engage men as well as women.
However, after 60 years, it is clear that it is the human rights of women that we see most widely ignored around the world, from female infanticide, sexual slavery and rape as an act of war, to exclusion from education, health and the right to compete equally for jobs. The right to be free of discrimination on the grounds of sex is specifically embodied in Article 2 of the declaration, but even a cursory reading of all 30 Articles is enough to remind us that in much of the world, the Declaration has yet to fulfill its promise to women.