Judy Blume 
Pain and the Great One [EPUB ebook] 

"The Pain" and "The Great One" are not their real names. But you may know their voices. When this girl, age eight, and this boy, age six, tell all about each other, they sound a lot alike. They are brother and sister and they’re caught in a contest over whom Mom and Dad love most. You probably know who wins, too, in this funny, family picturebook.