There have been endless articles written about strong-willed children.

How to parent them.

What a blessing they can be.

What ages are the hardest.

The likelihood of whether they’ll end up in jail or not.

But there’s something pretty remarkable about those strong-willed kids—they make their siblings stronger, too.

Before my daughter turned one and her true personality shined brighter than any diamond in the whole world, my son (her big brother) was a cautious, rule-following, soft-spoken boy. But when his sister started talking the talk and walking the walk, he learned that he’d need to fight to keep his spot in the family. And fight, he did.

When my feisty daughter first started sassing her big brother, he acted pretty aloof. I remember them playing in their little kitchen and every pretend piece of food my son would cook with, my daughter would grab out of his hands. He’d throw me a look like, “Who invited this girl to the party?” But he’d shrug it off and continue with his day. Yet, the more she interrupted his day, the more ticked off he’d get. He started to grab that pretend food back out of her hands or use his words to defend his turf. Finally, my son began sticking up for himself and our late-talker began using that voice of his.

In preschool, his teacher said he acted pretty timid in class when he was three. He listened, took turns, and followed the rules, of course—but he seldom talked. Shy, introverted—whatever you want to call it—the kid rarely spoke. But after a year of putting up with his strong-willed sister at home, things began to change when he turned four. He became vocal, active, and even competitive. Yes, he was still mostly an introverted rule-follower at school, but the teacher said he was making friends. Then one day around the holidays, I went to pick him up from school. His teacher waved me over to tell me a story.

“You’ll never guess what Anderson did today?” she said. “I was going to open the book Frosty the Snowman to read to the class and Anderson raised his hand telling me that he could recite it to the entire class. He did.” Pride beamed out of my pores and filled every inch of that classroom. I stood speechless and tears filled the brims of my eyes. My bashful son acquired the courage to recite an entire book in front of his peers.

And today, my son is competitive—even aggressive—in sports. He’s excited about academics, shares aloud in his kindergarten class, and sticks up for himself when someone wrongs him. You see, his aggressive little sister makes him fight for stuff. The arguing, it gets on my nerves most of the time, but in hindsight, she’s given him confidence.

See, strong-willed children are born with that will to fight—self-assurance that can’t be shattered. They stand stubborn and will beat you in any contest you throw at them. With one look, the strong-willed child will destroy any parenting tactic you think will work. Yes, strong-willed children were born to crush that parenting self-esteem of ours. But, they’re also teaching their siblings a thing or two.

I wonder how my son would be today if he didn’t have a little sister like he does. Would he still be a nervous wallflower? Would he make friends? Would he have that competitiveness inside of him? Maybe. But I do know that my daughter has helped bring all of that out of him, too. If you look deep enough, that child and their will to drive you insane is also giving your other children the gift of confidence—something that will last them a lifetime.