How is a mild-tempered, cooperative child likely to be impacted by the presence of a defiant and strong-willed sibling in the home? My oldest daughter is a model child – pleasant, cheerful, and agreeable. Her brother is the exact opposite. I may contact you about him some other time; believe me, there's plenty to say. But for the time being I can't help feeling concerned about the effects his behavior and personality may be having on his sister. What do I need to know about the unique needs of a quiet, compliant child?