M any people were shocked when Dustin and I surprised the boys last Halloween with a puppy, just three weeks before Dustin left for his deployment. “Are you sure you want to take on the extra responsibility?” they said. And, “Do you know what you’re getting into?”

What most people didn’t know, however, was that we had a 4-year-old who believed he was a dog, to the point of eating off the floor and carrying a tennis ball in his mouth.

Before Sparky, the last dog we lived with was a border collie named Annie, who, I suspect, could manage pre- Algebra. She was one of the smartest dogs I’ve ever known, except for that time she ate an SOS pad. But Annie also liked to eat wood — specifically, our back porch — so she left us to work on a 13-acre farm in Florida.

Lindell never knew Annie.

We had a long, pet-free period (unless you count fish), until one year ago when the boys ran from the schoolyard to greet the new puppy waiting for them on the sidewalk. So long as Sparky wasn’t on a mission, like Annie, to destroy every single thing we own, I knew he would be a welcome addition.

Yes, even though Dustin was leaving.

You see, as it turns out, Sparky, a Brittany Spaniel, has been a great distraction, especially for Lindell. Sparky has been cried on, hugged (perhaps too tightly) and fought over (“He’s sleeping in my room.” “No, my room!”). Sparky even was an accomplice to the great “runaway episode” several months ago. I can’t say which one, but “a son” ran away to the end of the street with no suitcase or change of clothes, but with a willing dog, who likes to go on walks, by his side.

Sparky has also done wonders for Lindell’s confusion about being a dog.

At first, Sparky and Lindell had some “getting used to” (Lindell’s words) to do. Sparky often sighed, and sometimes ran away, when Lindell came near. This might have had something to do with the Scooby Doo costume Lindell wore and the fact that he took naps in Sparky’s bed — usually on top of Sparky.

Eventually, however, Lindell

“learned Sparky’s lessons” (again, Lindell’s words), and besides that time Sparky ran out the backdoor with Lindell’s underwear, the two seldom make each other cry. They have settled into a nice, passive-aggressive relationship of sibling rivalry.

Sparky has brought out many aspects of all my boys’ personalities. Lindell is the needler, the instigator. He is not opposed to blaming his mess on Sparky. Ford is the dutiful helper, always willing to take Sparky for a walk or feed him breakfast. Owen is the empathizer. When Sparky had to wear the dreaded “cone of shame” (a postsurgery e-collar) last week, Owen hand-fed his meals to him.

Just as a husband and wife unite in their children, the older boys and I have bonded over our shared love of Sparky. When we pick up Sparky after a bath or time spent playing with another dog, Ford and Owen smile uncontrollably.

“Look at him just sitting there with those other dogs,” they say. Or, “Look at how smart he is!”

This reminds me of human parents’ behavior when they pick up their children at school. Also, it reminds me of the way Ford and Owen act when they see Lindell playing at the park with friends.

Lindell doesn’t participate in these loving observations of Sparky, because he doesn’t view Sparky as a “child.” He sees him as a brother. While Lindell has moved past believing he himself is 100 percent dog (it’s been a long time since he carried a tennis ball in his mouth), he and Sparky are still, in many ways, growing up together. They are in parallel states of innocence and wonder.

I wish I could suspend them there.

Soon, Lindell will move past Sparky (age- and experience wise), even though I know he will never outgrow him. There will always be a little piece of Lindell that is part-Sparky/dog.

Which brings me back to Lindell’s species identity.

When my mother-in-law, Robin, was visiting last month, she told the boys about a new way to study genealogy. Using a test-tube provided by a scientific company, Robin sends a sample of her saliva to be analyzed for DNA. The results tell her what percentage of her DNA is European, Middle Eastern, etc. Ford’s and Owen’s eyes lit up at the thought. Later, they asked me, “Can we do this with Lindell and add a little bit of Sparky’s spit before sending it off, so that the results come back with ‘You are 10 percent dog’?”

I laughed. And then I felt sad. If that could actually work — if it would keep my two youngest boys, Lindell and Sparky, in a suspended state of blissful innocence — I just might try it.

NAVY WIFE Sarah Smiley is the author of Shore Duty, a syndicated newspaper column that reaches more than 2 million readers weekly, and of the memoir “Going Overboard: The Misadventures of a Military Wife” and a collection of essays titled “I’m Just Saying …” For more information visit www.SarahSmiley.com.