Clockwise from left: Zephyr, Zephyr, and Zephyr

A group of fish is a school. A group of lions is a pride. What should a group of Zephyrs be called?

This is one question for the families of Zephyr Cossairt, Zephyr Balch and Zephyr Vehlo, three young men living within a mile of each other in Evanston.

It seems a reasonable bet that this is the only square mile anywhere with three resident Zephyrs.

Zephyr Cossairt, now 2 years old, was delivered in 2016 with the help of a local midwife, Sarah Simmons. When Stephanie Hunt and her husband Oliver Cossairt told Ms. Simmons the baby’s name she was startled. “Really? Zephyr? I know another Zephyr in Evanston,” she told them.

Ms. Simmons put small Zephyr’s parents in contact with Dori Conn and this writer, the parents of Zephyr Balch, age 17. Soon thereafter large Zephyr became a principal babysitter for small Zephyr and his brother Elio, age 6, and sister Asha, age 8.

“It can get confusing,” said large Zephyr, who also has a sister, Maple Conn, age 19. “When Elio and Asha call our name we both look around and at each other.”

Two years after the two families met, Ms. Conn was at the McGaw YMCA and heard a woman calling “Zephyr” to youngsters in the gym.

“I glanced around for my own Zephyr,” said Ms. Conn, “but realized he couldn’t be in the building. And I saw that the woman wasn’t small Zephyr’s mom, and that the boy she was talking to was medium-sized. I introduced myself and explained that I have a Zephyr, too.”

The woman was Valerie Vehlo, who, with husband Tiago, are the parents of medium Zephyr, age 9. Unlike the other two Zephyrs, who live on the same street a half-mile apart, medium Zephyr and family live on a different street – but still within a mile.

“Pretty cool,” said large Zephyr,­ “but I’d rather have us all on the same street.”

How was each Zephyr’s name chosen?

In large Zephyr’s case, the goal was to commemorate a relative with a Z name.

“We liked the connotation of a gentle breeze,” said Ms. Conn, alluding to Zephyros, Greek god of the West wind.

Zephyros was also on the minds of medium Zephyr’s parents, as Valerie is of Greek descent. Tiago, originally from Brazil, appreciated that the ancient name has a cognate in Portuguese. Medium Zephyr has a sibling as well, Dylan, age 7.

Small Zephyr’s parents were likewise drawn to a Z name.

“We were thinking of the name for our second child,” Ms. Hunt said, “but he was born very blond and seemed more an Elio [a name related to the Greek root for Sun].

“Then Zephyr was born in early summer and it felt like the right name – I knew he’d be our last and it was nice to have an ‘A’ kid and a ‘Z’ kid.”

While none of the families plans more children, if current trends continue a fourth Zephyr will arrive in the area in about six years.