This article analyzes the interplay between policymakers and scientists in developing the Family Policy Plan for the Czech Republic in 2017. As former members of the government commission that developed the plan, we base the article on participatory observation. When we joined the commission, a 'window of opportunity' had opened as the country for the first time ever had feminist-friendly minister and vice-minister of labour and social affairs. We explain why due to the inter- and intra-party dynamics, the parental leave reform to introduce 'daddy months' failed. We argue an adversarial subsystem existed in that the three coalition partners disagreed on the reform. According to Ingold and Gschwend (2014), under such circumstances, scientists play a strategic role, especially if there is unity among them. However, although there was basic unity among the scientists in the commission, the coalition partners at the governing level were able to block or water down the reform proposal under the study.