Q: Our 5-year-old has never been a good sleeper, and now we have a new baby who is 6 months old. How much sleep do most 5-year-old children need? The baby is not sleeping through the night yet, and we are terrified that we will have the same sleep issues with her. My sister says that at some point you have to just let them "cry it out," and they will be better sleepers. Can you help?