Their son Oliver is born through the events of "Galentine's Day" in Season six. In the sequence finale, it is revealed that Oliver has a younger sister named Leslie, presumably immediately after Leslie Knope. When Leslie, Ron, April and Andy are in London, it is unveiled that Diane instructed tagging together to make the journey hers and Ron's honeymoon, but her morning illness intended that she couldn't go. Littleton, Cynthia (April 29, 2019).