Adults in the United States are having fewer biological children in part due to worries about climate change and population growth, yet Christian environmental ethicists frequently avoid or dismiss these “eco-reproductive” concerns. I argue that these avoidances lead to important limitations in the literature, which I address by employing a pragmatic approach for religious ethics. Learning from environmentalists who are critically engaging with their Christian inheritances, I find that informants draw upon religious repertoires to “kinnovate.” Namely, they expand notions of family beyond biological lineage by taking up vocations as godparents, youth mentors, foster parents, or chosen kin. I claim that these practices of Christian kinnovation are significant because they help to advance creative moral responses to eco-reproductive concerns in religious contexts—interventions that currently remain underdeveloped in relevant ethical and theological literatures.