The frightening logic every child secretly runs when a sibling arrives

Ask most parents why their children fight, and you'll get answers about toys, or attention, or who got the bigger slice of cake. Adele Faber and Elaine Mazlish went looking for something underneath all of that, and what they found runs deeper than any single argument.

According to the experts they consulted, at the root of sibling jealousy sits one desire: to be the exclusive object of a parent's love. Not shared love, not love divided into equal portions. Exclusive. Because everything a small child needs to survive and grow, food, warmth, a sense of being worth something, flows from a parent, that love isn't a nice extra. It's the sunlight the child grows in.

Which means another child in the house isn't neutral news. It reads, to a child's nervous system, as LESS. Less time alone with a parent. Less attention when something hurts. Less applause for a picture proudly held up. And underneath that sits a darker thought most children never say aloud: if my parents are lighting up this much over my brother or sister, maybe he or she is worth more than me. And if they're worth more, I must be worth less. And if I'm worth less, I'm in trouble.

That's the calculation Faber and Mazlish describe running quietly under so much of what looks like ordinary bickering over crayons and car seats. It explains why children fight so hard to be first, to be best, to have more, or better yet, all of the food, the toys, the space, the parent. Security, to a child, can look like having everything, because having less has started to feel like being loved less.

Once you see the arithmetic this way, ordinary flashpoints look different. A child screaming that his sister got a bigger cookie isn't really negotiating cookie size. He's checking whether the world still has enough love in it for him. Parents can't erase this instinct, but naming it, and answering it directly instead of dismissing it as childish nonsense, is where the real work of easing sibling rivalry begins.

Start by noticing the moments when your child seems to be testing whether there's still enough of you to go around, and instead of brushing the moment off, name what's underneath it out loud, telling her plainly that she is safe and special to you in a way nobody else can be. When you catch yourself about to say something that implies one child is getting more, more time, more praise, more anything, pause and ask what your other child might be hearing in that moment. Look for small, private ways across the week to remind each child that your love for them was never a slice cut out of a fixed pie, but something that grew the moment they were born, with no shortage in sight.