That’s how it goes in a pack of siblings, and I sometimes wonder, when it comes to the decline in fertility rates in our country and others, whether the economic impact will be any more significant than the intimate one. For better or worse, fewer people will know the challenges and comforts of a sprawling clan.

Those comforts are manifold, at least in my lucky experience. With siblings to help shoulder the burden of your parents’ dreams and expectations, you can flail on a particular front with lower stakes and maybe even less notice. Siblings not only pick up the slack but also act as decoys, providing crucial distraction.

They’re less tailored fits than friends are. But in a family that’s succeeded at closeness, they’re more natural, better harbors. As Colt observed of his siblings, and it’s true of mine as well, they aren’t people he would have likely made an effort to know or spend time with if he’d met them at school, say, or at work. And yet a reunion with them thrills him more than a reunion with friends, who don’t make him feel that he’s “a part of a larger quilt,” he said. His brothers do.

My friend Campbell, who’s as fond of her two sisters as I am of my siblings, put it this way: “With a friend, I have to be more articulate. With my sisters, I can be my most primal self: inarticulate, childishly emotional. I’ll have a fight with my sister and say, ‘O.K., I know we’re in a fight, but I need your advice on something,’ and we can just put the fight on hold. They’re the only people in the world you can be your worst self with and they’ll still accept you.”