Korean families have been undergone tremendous changes during the past three decades with societal changes. Korean families become smaller, diverse, and multi-cultural. These family changes challenge child development research. Family is not just an intimate relationship. Family is also a structural environment, a system linking micro and macro system, an institution, and an ideology. Consequently, researchers need to pay attention to various ways family influence child development and take into account family as a whole unit. Researchers are also challenged to make a stance regarding family changes and diversity. Temporality is another important issue in studying how family development and child development interact. In terms of public policy, social services should be developed to cope with the new social risks from family changes and to mitigate a growing developmental gap among the children of families with different economic classes.