Social communication deficits are a core symptom of autism spectrum disorder (ASD). The present paper reviews 54 studies evaluating social communication interventions delivered by parents and siblings to children with ASD under 6 years old. Fifty studies evaluated parent-mediated intervention, and four studies evaluated sibling-mediated intervention. Fourteen studies evaluated interventions using telehealth. Treatment effects and research strength were variable across studies. Treatment modality, setting, and dosage had inconclusive impact on treatment effect. Parent-implemented intervention packages, Pivotal Response Treatment (PRT), Early Start Denver Model (ESDM), and Joint Attention, Symbolic Play, Engagement & Regulation (JASPER), qualified as established evidence-based practice for this population. Most studies reported successful generalization of skills for some, but not all, children. Telehealth and sibling-mediated intervention are promising areas of further research and clinical practice.