Youth sport participation can lead to stressful experiences for athletes, and the way such emotions are regulated have profound implications for their experiences and continued participation. As one of the most prominent socialization agents for youth, parents and family members are in a unique position to help regulate their youth athlete's emotions that arise in sport. The purpose of this study was to examine the emotion regulation dynamics within competitive sport family-units. Using an interpretive case study approach, semi-structured interviews were conducted with two family-units, including competitive male youth athletes (n = 2; Mage = 11 years), their parents (n = 4; two males and two females; Mage = 44.5 years), and one male siblings (n = 1; 15 years old) to better understand the developmental implications of familial emotion regulation in youth sport. Following reflexive thematic analysis, two defining themes were generated from each case. In one family, the sport transition of one athlete marked a pivotal change in the family’s identity and the roles each play in emotional experiences. Conversely, parents from the second family-unit discussed effort as a central underlying value for their family’s sport involvement, which led to different regulatory strategies in private and public settings. Theoretically, generated themes provide novel insight in youth sport contexts and align with the tripartite model of family impact on children’s emotion regulation. For applied scholars, the findings highlight the importance of empowering parents with adaptive co-regulation strategies for the continued participation and development of their athletes.