Vocal plasticity is the ability of an individual to modify its vocalizations according to its environment. Humans benefit from an extreme form of vocal plasticity, allowing us to produce a wide range of sounds. This capacity to modify sounds has been shown in three bird orders and in a few nonhuman mammal species, all characterized by complex vocal communication systems. In other mammals, there is no evidence for a social impact on vocal development. We investigated whether contact calls were affected by social environment and kinship during early ontogeny in goats, a highly vocal and social species. To test the influence of social environment on kid vocalizations, we compared half siblings raised in the same or different groups. The effect of kinship on calls was assessed by comparing full siblings with half siblings. Calls of half siblings were more similar when they had been raised in the same social group than in different groups, and converged with time. Full siblings had more similar calls than half siblings. The group-specific indicators in kid vocalizations show that goat call ontogeny is affected by their social environment. This suggests that vocal plasticity could be more widespread in mammals than previously believed, showing a possible early pathway in the evolution of vocal learning leading to human language.