Three-year-old Molly's life was perfect. She was the center of attention in the perfect love triangle: mommy, daddy, and child. She had her parents' complete attention her whole life long and she knew exactly what to expect. She never had to share her parents with anyone.
Then into her life comes an intruder, threatening to take her place at center stage. A star is born! The audience "oohs" and "ahhhs" over this younger rival and showers him with gifts. Molly is no longer the most important member of the family. As she bids for equal time she hears, "Not now, I have to nurse the baby." When guests arrive, she gets passed over in favor of "Oh, what a beautiful baby." Her disappointment at her apparent demotion escalates into anger at this little upstart who unseated her, and she is confused because everyone is telling her how lucky she is to have such a nice baby brother.
Many parents in this situation will try to smooth things over with adult logic. But before they do, they should consider how the situation looks through the eyes of their child: "Think on the bright side. You've gained a playmate." (Child's logic: "I've got plenty of playmates. Did I ask for another one? And this one can't play—all she does is cry.") "Mommy and daddy love you just as much." ("Then why is that baby always in your arms and I'm not?") "I need to spend more time with your baby sister because babies need mommies so much, just like you did when you were a baby." ("I'd rather still be a baby. And I need mommy, too. Besides, I don't remember being a baby.") "Mommy's busy, but you and daddy can do something special." ("Why did you need a baby? Wasn't I good enough?") "You'll get used to her, and she'll be fun to play with." ("I hate that baby. That baby upsets all my fun. When can you take the baby back, mommy?")
After months of this wishful thinking, reality hits. The baby isn't going back. In fact, she's growing up, crawling, and getting into the older child's precious possessions. So the child digs in to defend her turf against the enemy who topples her towers of blocks and pesters her playmates. Big sister spends the rest of her growing-up years competing for the family prize – her parents' attention.