Already in the beginning, this study points out that members of sexual minorities still have to cross hurdles towards full equality and a life without discrimination in western countries. For example, there are often restrictions on joint adoption by same-sex couples or state recognition of their partnerships is not yet given everywhere. As legislative bodies, parliaments play a decisive role in establishing legal equality. Therefore, the following comparative case study aims to provide an answer to the question of why parliaments as a whole substantively represent the interests of sexual minorities.