Oonga Boonga by Frieda Wishinsky

This is a great book for an older sibling who is having a difficult time adjusting to a new baby in the house. Baby Louise cries all of the time and nothing her parents or grandparents do can make her happy. But when her older brother Daniel comes home and starts to whisper funny words into her ear she stops when he says "Oonga Boonga!" Baby Louise is all smiles when her brother is around, but as soon as he goes out to play she starts to cry and again, and even though her parents and grandparents try to say "Oonga Boonga" in just the right way, she won't stop crying until Daniel comes inside and whispers new phrase into her ear. The book offer a wonderful lesson about how important siblings can be to one another and why a big brother or sister can be the best friend a baby can have.