This study investigated parents' and siblings' knowledge use during naturalistic teaching episodes in the home. Thirty-seven middle-class families were observed for six 90-minute sessions (siblings aged 4 and 6 years). Parent and sibling teaching sequences were coded for knowledge type (conceptual, procedural), conceptual subcategories (social conventional behavior; game discussions; academic concepts; problem solving) and procedural knowledge subcategories (game procedures; general skill procedures). Research Findings: Findings indicated no significant mean difference between mothers' and fathers' and older and younger siblings' conceptual and procedural teaching. However, parents taught proportionally more conceptual knowledge than siblings, indicating that siblings taught proportionally more procedural knowledge compared to parents. In terms of conceptual subcategories, parents taught more social conventional behaviors, whereas siblings taught more academic concepts. Siblings also taught more general skill procedures compared to parents. Practice or Policy: Overall, our findings indicate that the home environment is a rich context for the naturalistic teaching of conceptual and procedural knowledge by both parents and siblings, thus advancing our understanding of the role of family dynamics on children's learning and development.