We investigate the spillover effects of early-life medical treatments on the siblings of treated children. We use a regression discontinuity design that exploits changes in medical treatments across the very low birth weight (VLBW) cutoff. Using administrative data from Denmark, we first confirm the findings in the previous literature that children who are slightly below the VLBW cutoff have better short- and long-term health, and higher math test scores in 9th grade. We next investigate spillover effects on siblings and find no evidence of an impact on their health outcomes. However, we find substantial positive spillovers on all our measures of academic achievement. Our estimates suggest that siblings of focal children who were slightly below the VLBW cutoff have higher 9th grade language and math test scores, as well as higher probability of enrolling in a high school by age 19. Our results suggest that improved interactions within the family may be an important pathway behind the observed spillover effects.