In the original Two Open Windows, Kim and Watamura (2015) highlighted research supporting the transition to parenting as a co-occurring sensitive period — in other words, as a time in life characterized by “two open windows” where both infants and parents are especially receptive to being shaped by their environments. Here, we provide an update of research for parents, policymakers, researchers, and practitioners to inform approaches to supporting families with diverse needs, compositions, and backgrounds within a two-generation framework.