Sport expertise is strongly associated with practice patterns throughout development, but early sport participation is shaped by parents as instigators, facilitators, and supporters of their child's sport engagement (Harwood, 2017). Further, parental experience and expertise in sport positively predicts athletes' peak levels of expertise (Wilson et al., 2019). This study explored the relationship between previous parental sport experience/expertise and the athletic trajectories of their children using a secondary analysis of athlete responses to the Developmental History of Athletes Questionnaire (Hopwood, 2013; n = 259; Mage = 22.9, 18-35). ANOVAs compared the age of the athlete at nine developmental milestones (e.g., first participated in practice with a coach) and the volume of sport-related practice accumulated each year prior to turning 18, according to indicators of parental sport participation. Parental participation in competitive sport, but not parental skill, was significantly associated with earlier engagement by the athlete in supervised (p = .011, ?2 = .025), unsupervised (p = .035, ?2 = .021), and physical training (p = .031, ?2 = .018), as well as the earlier emergence of the idea of becoming an elite athlete (p = .013, ?2 = .025). Significantly (p <.05) more sport-specific practice was accumulated each year between ages 5-12 by children of parents who participated in regular competitive sport, and competed at a non-elite level. Athletes' developmental trajectories appear to be significantly affected by their parents' sport experiences, a potentially potent antecedent of sport expertise in need of much greater depth and breadth of investigation.