A: You are right that you must protect your 10-week-old daughter. It is possible that your nephew is very jealous of the new baby and that his jealousy is making him aggressive. Try asking your sister to set aside time to share a cup of coffee, just the two of you (have someone else mind the children for an hour). Then, be honest about your concerns and explain that you would really appreciate her help in creating a calmer atmosphere. Explain that her son's energy level feels disruptive, even though you know that he's a great kid. Put the emphasis on your need for peace and quiet. If your sister gets annoyed, you may not be able to get through to her. If you can't make your sister an ally, you will just have to watch the situation like a hawk to make sure nothing bad happens.