Pain and the Great One

“Sometimes I think Mom and Dad love her more than me.”—The Pain
 
“Sometimes I think Mom and Dad love him more than me.”—The Great One
 
The Great One thinks her brother, the Pain, is a messy slowpoke who gets dessert even if he doesn’t finish dinner. She thinks her parents love him more than they love her. The Pain thinks his older sister, the Great One, is a bossy know-it-all. Just because she’s older, she gets to feed the cat and play real songs on the piano. He thinks his parents love her more than they love him.
 
How will they ever find out who is loved more?