From 1979 to 2012, the Chinese government implemented the one-child policy to control population growth. In 2013, families in which either parent was the only one child were allowed to apply for a second child. In 2016, China's universal two-child policy was finally imposed. As such, many children who had always been the center of their family's universe due to the unique family structure stemming from the one-child policy era became elder siblings during their adolescence. We report a case of a 9-year-old girl who developed seizures after the birth of her younger sister. The combination of clinical observation, laboratory examinations, and video-electroencephalography was not enough to make a confident diagnosis of epilepsy initially. Given her patient history and follow-up investigation, we speculated the two-child policy was related to her seizures. To our knowledge, this is the first report of seizures strongly related to the two-child policy.