Sarah Beverly Koatz and Stuart Hopkins Winchester had no idea where their relationship was going in March 2013, but the “Cupid Cabbie” did. By the end of their yellow taxi ride one evening from Union Square to the Upper East Side in New York, he told them they would get married someday.

“I was so embarrassed,” said Ms. Koatz, who met Mr. Winchester in 2004, when they were just 15, at camp in the Berkshires, and then became best friends after college. “I didn’t know if we were dating or not.”

Ms. Koatz, 31, now a licensed clinical social worker at NewYork-Presbyterian/Weill Cornell Medical Center, graduated from Bates College in Lewiston, Me., and received a master’s degree in social work from Columbia.

Mr. Winchester, also 31, is the chief executive of Marble, a technology company that helps people organize insurance documents and provides rewards points. He graduated from Trinity College, University of Dublin.

The couple met briefly in 2004 at Becket-Chimney Corners YMCA summer camp in Becket, Mass., before going on international community service trips — she to Valparaiso, Chile, and he to an aboriginal community near Alice Springs in Australia.

“We were both camp lifers, and saw each other at camp or sometimes in group hangouts during the year,” Mr. Winchester said. In 2005, at dinner with friends in New York, while she was at Hunter College High School and he at Collegiate High School, they recalled kidding around about stringing two cans together over Central Park to talk to each other, from her home on the Upper East Side to his on the Upper West Side.

During college they dated other people, and were “friendly acquaintances,” she said, but in 2011, after they graduated, they became best friends while living in New York.

“Stuart and I have always been on the same page,” she said. “We have the same sense of humor,” and he would even go as far as saying “she’s definitely funnier.”

They went out, first as part of a group, but then just the two of them. They spoke just about every day, and saw each other every weekend.

“It became clear something was happening outside the friends’ groups,” he said.

But when they had a first kiss while out one evening, they quickly decided to stick to being best friends a little while longer.

“It had been existing without a label, but we were in a relationship,” said Mr. Winchester, so it came as no surprise to their parents when they made it official in March 2013. While things were still a bit tentative, they got into Ahmed Ibrahim’s yellow cab, which they said wasn’t like any other cab.

“‘I’m known as Cupid Cabbie,’” he recalled Mr. Ibrahim saying, and by the end of the trip, he gave them a rundown of successful matches. “‘You guys seem very good together, and I think you’re going to get married.’ We laughed about it, and forgot about it until we got engaged.”

Mr. Winchester proposed New Year’s Eve 2019 in their Upper West Side apartment, and later that evening their New Year’s Eve/housewarming party there turned into an impromptu engagement party.

“We’re major homebodies,” Ms. Koatz said, adding that they love taking care of their Ragdoll cat, Murray, their plants and home.

They planned to get married Oct. 10, mainly because of the symmetry of the 10/10/20 date, in Mr. Winchester’s parents’ backyard in Bedford, N.Y., once an apple orchard, and expected about 100 guests before the coronavirus.

On the day “Cupid Cabbie” knew was inevitable, the Rev. Deborah Steen Ross, an interfaith minister, led the ceremony with her husband, Rabbi Roger Ross. Their 45 guests, who wore cream-colored masks embroidered with “10/10/20,” watched along with about 100 others via Zoom.