My youngest son, Lindell, 4, has had just one aspiration: to be a dog. I’m not joking. Neither is he.

Before Lindell knew his ABCs, he was fetching a tennis ball … with his mouth.

Oh, I had tried to stop this behavior, and I put my foot down when he asked to be fed from a bowl on the floor. But soon it became obvious that Lindell really does have a deep affinity for animals, specifically dogs. We bought him stuffed animals and even live fish (Note: a fish is a not a dog). These only satisfied Lindell temporarily.

Then Lindell started asking us to refer to him as Scooby. He pawed at my thighs while I was washing dishes and he licked Dustin’s face. When he called me “Daphne” in the middle of Kohl’s, and I replied reflexively, “Yes, Scoob,” onlookers stifled their laughs.

Sometimes Lindell switched and asked us to call him “Sparky.” Eventually, however, “Sparky” became the name Lindell said he’d name his own dog, the one he was sure he’d get someday soon.

“Not now,” Dustin said. “There’s no chance we’re getting a dog.”

“Are you sure, Dustin?” I said after Lindell went to bed. “Think about how excited the kids would be.”

“No. Not a chance. It’s not the right time.”

That was early October. Slowly, I began pressing Dustin: “Maybe a dog would help Lindell overcome his habit of fetching tennis balls. Maybe he’d stop asking for Scooby Snacks. And his older brothers are always busy doing other things; a dog would be a playmate for Lindell. I’d take care of it, of course. You wouldn’t be responsible for anything. I’d even clean up all the, um, you know.”

“No. Not a chance. We’ve already talked about this.”

A week later, Dustin went to the Humane Society after work to pick out a dog for me. The one he had his eye on had already been adopted. When Dustin came home and told me this, I secretly marveled at my powers, powers I’d like to harness. How did I bring him from “no” to “how soon can we get a dog” in the course of one week? Because there are plenty of other things I want, too.

By the week of Halloween, we had found another dog. We didn’t tell the kids. In fact, as late as the day before we got our new dog, I told the boys again, “Stop asking for a dog! It will be a while before we can get a dog!”

And then, 24 hours later, we surprised them after school.

I believe there are moments in our life we never forget, snapshots stored away in our permanent memory. The look on Lindell’s face when he first saw Sparky is, for me, one of those moments.

That first night, Sparky got a taste of his new life: constantly being petted, chased, followed, tugged and stalked by a little boy in a Scooby Doo costume. The two dogs even took a nap together on Sparky’s pillow.

Then a funny thing happened, something only Dustin claims to have predicted. Lindell became jealous of the dog. He wanted his own leash and collar. He wanted his own crate. He was sad that everyone pet Sparky more than they pet him.

We had tapped into a new realm of sibling rivalry. And after a quick search on Amazon.com, there isn’t even a self-help book for dealing with this. Maybe we are the only ones with a son who thinks he’s a dog and is jealous of his family’s real dog.

“I think Lindell is just now realizing he’s not actually a dog,” Dustin said.

But sometimes, struggling is a good thing. Every first-born child is made stronger and more tolerant by the arrival of a new sibling. And so it will be with Lindell and Sparky. Already, they are easing into their new roles. Sparky is accepting his doghood, and Lindell is accepting his humanness. And all the while, a new friendship is forming between the two species. Sparky is the first thing Lindell looks for when he wakes up in the morning. And Sparky never misses a chance to sniff Lindell’s grubby pants and hands. He is fond of grabbing Scooby’s stuffed costume tail and following him around the house that way. Lindell is barking less, no longer chasing his “tail” and responding to “Lindell” more. If we never could get him trained, it looks like Sparky might.

A week later, I was petting Sparky on the living room floor and said over my shoulder to Dustin, “So, what changed your mind about getting a dog? How did I convince you in just a week?”

Dustin hesitated, reluctant to give me insight into my powers. Because that would be like letting a dog see from which pocket he gets his treats.

I turned around to look at Dustin. “Seriously, why did you decide to get me and the kids a dog?”

Dustin smiled and reached out to pet Sparky. “Because you only live once,” he said.

Yes, I think even Dustin has found a best friend in Sparky.

Sarah Smiley is a syndicated newspaper columnist, author and military wife. Her columns appear the second, fourth and occasional fifth Friday of each month.