Latinos have had the highest teenage birthrate of any racial or ethnic group in the United States for the past 15 years, yet little is known about how Latino families are affected by a teenage daughter's childbearing. In-depth interviews were conducted with 32 Mexican American younger siblings of parenting teens to discern how their sister's childbearing had affected them and their families. The most commonly reported negative effects were increased family stress and conflict, more arguments with the parenting older sister, and less time spent with family members. Regarding benefits, all youth described a loving bond with their sister's baby, two thirds described their family becoming closer, and 81% felt closer to their older sister. The implications of these effects for Mexican American families are discussed. (Contains 2 tables and 1 note.)