Like so many of the classic Manhattan love stories, this one involves real estate, and a Broadway tune.

Those are the twin passions of Tom Postilio and Mickey Conlon, who grew up a dozen miles apart on Long Island, both immersed in the music of an older generation.

Eventually, they found their way to each other, meeting for the first time under a theater marquee and joining not only their soundtrack collections but their careers, as luxury residential brokers. Their clientele — and social circle — includes Liza Minnelli, Barry Manilow and Joan Collins; they are among the most notable sellers at Douglas Elliman, with cumulative property deals in the billions, and have their own spotlight as stars of “Selling New York,” a reality show on HGTV.

Dapper, handsome, with the crisp manners and suave wit of MGM-era heroes (think Cary Grant or Fred Astaire), they’re adept at making others feel at ease, said their friend Christine Ebersole, the Tony-winning actress and singer. “When you’re around them, you just think anything is possible,” she said.

The musician Michael Feinstein, a close friend who listed his 18-room home for sale with them a few years ago, noticed their spark right away. “Sometimes you see a light in someone’s eyes, and it’s a subtle change at first, and then it manifests more and more as two people are together,” he said. Couples, he added, find an emotional equilibrium, but it can be low as often as high. “With Tom and Mickey, they truly elevated each other,” he said.

Theirs is a life purpose-built for duets: “Me and My Shadow” is their signature. To their friends and audiences, they are always Tom and Mickey, never Mickey and Tom, with trademark bow ties for Mr. Conlon, and straight ties for Mr. Postilio. If their romance were a musical, we’d see it developing in tandem across the stage, with just the slightest hint of a twist near the 11 o’clock number.

By the time Mr. Postilio, 46, moved to Hauppauge from Queens with his family in high school, he already had throwback tastes. “While everybody else was listening to Guns N’ Roses and Def Leppard, I was running around in Frank Sinatra T-shirts, singing ‘Strangers in the Night,’ ” he said. In 1984, his family had gone to see Sinatra at Carnegie Hall. “For a 14-year-old from Ozone Park, Queens, it was like being hit by a lightning bolt,” Mr. Postilio said. His father, Leonard Postilio, faithfully indulged his obsession by taking him to Sinatra conventions, while worrying a bit about where this fandom would lead.

But his son had an angle: He sounded just like Sinatra, or as alike as a teenager could. He began entering and winning singing competitions and, at 20, was hired as a vocalist with the Glenn Miller Orchestra. He earned an associate degree at Suffolk Community College and left to tour the world with the band.

For more than a decade, Mr. Postilio lived by the Great American Songbook, singing on cruise ships and with symphony orchestras. He released two albums and had an 18-month run in the Off Broadway revue “Our Sinatra.”

“One thing I admire about Tom,” his father said, “he has that stick-to-it-iveness.”

Meanwhile, Mr. Conlon, 39, the youngest of three, was raised in St. James, where he too developed out-of-sync favorites. “I would do Al Jolson impressions at 7 years old,” he said, and “run home to watch ‘Singin’ in the Rain’ if it happened to be on TV.”

And by his teenage years, he was already an adept entrepreneur. At 16, with his mother, Mary O’Rourke, as a co-signer, he opened an antiques shop in town. He took her to auctions, she recalled, where he knew just what to scoop up and resell for a profit. “He always had an eye for that,” she said.

At 18, he got his real estate license, showing classic homes in his first summer off from Duke University. He had wanted to be a lawyer (he studied political science) but had a change of heart when he also discovered theater producing in college, a way to bridge his business acumen and his showmanship.

Back in New York, Mr. Conlon worked on musicals like the Tony-nominated “Jane Eyre” and “Xanadu,” but the 2008 recession made him rethink his trade, and he rebounded to real estate. Mr. Postilio had landed there, too, after his singing gigs dried up in the early 2000s. He was a founder of a boutique brokerage firm and began appearing on “Selling New York.”

Though they were professionally successful, neither felt he had mastered relationships. “I was never much of a serial dater,” Mr. Conlon said. “To that extent, I consider myself shy.”

On the road, Mr. Postilio rarely had time for dating, and when he changed professions, his retro style made him an outlier. One boyfriend openly recoiled from his musical taste. “He said: ‘Can we change the music? I feel like I’m at my grandmother’s apartment,’” Mr. Postilio said. “And I think I broke up with him the next day.”

In January 2008, a mutual friend, the entertainment lawyer Mark Sendroff, invited them to the Nightlife Awards, a gala to honor cabaret, jazz and comedy stars. It was a frigid Monday, and Mr. Conlon balked at venturing out, but Mr. Sendroff persuaded him with the lure of seeing Marilyn Maye, the veteran singer, who was almost 80 at the time. He and Mr. Postilio were introduced under the klieg lights of Town Hall in Midtown, a moment both remember lyrically.

Mr. Postilio: “I was mesmerized by the sparkle in his eyes.”

Mr. Conlon: “I thought, ‘Here’s a kindred spirit.’”

They chatted at intermission and through the after-party, and then Ms. Maye swept them up to Birdland, where Tony Bennett was on the bill. They were already en route to becoming Tom and Mickey. “Our courting period was Town Hall to Birdland,” Mr. Conlon said.

Their first official date came just a few days later, and long before the year was out, Mr. Conlon had moved into Mr. Postilio’s apartment. (Mr. Sendroff and Ms. Maye, who is still performing, both take credit for the match.)

Their families met quickly, too; Mr. Conlon’s stepfather, James J. O’Rourke Jr., died four weeks after Mr. Conlon began dating Mr. Postilio, and Mr. Conlon was touched that Mr. Postilio and his mother, Eileen, came to the funeral. “Suddenly, I had a new support system in Tom,” he said. “I thought, ‘This is a real, grown-up relationship.’”

Eileen Postilio said: “I liked Mickey right away. It just took off. They’re so alike, my husband called them the two-headed monster. They’re usually on the same wavelength.”

Their force multiplied in 2011, when Mr. Conlon, then working at Brown Harris Stevens, decided to join Mr. Postilio at his firm, CORE. (They migrated to Douglas Elliman last year.)

They did their due diligence before teaming up. “We talked to a bunch of couples who worked together,” Mr. Conlon said, and they made a pact that their relationship came first. “We said, ‘If we’re bickering and we take it home with us, we’ll go back’” to separate jobs. But, he added, “instead of taxing the relationship, it made it stronger.”

Their entertainment backgrounds are also a major asset: Mr. Postilio has been known to break into song to close a deal. “We always joke that, in the end, it’s all showbiz, kid,” Mr. Conlon said.

Almost four years ago, they bought their first property together, on the North Fork of Long Island, with an eye toward rebuilding it. They had discussed marriage, and on Christmas 2013, standing atop the roof, looking out over Long Island Sound, Mr. Postilio proposed.

They envisioned a grand summer wedding at that Long Island estate. But construction stalled, and they decided not to prioritize a renovation over their commitment.

A few weeks ago, they very nearly eloped, asking Mr. Feinstein to be their witness at City Hall. But the calendars didn’t quite align, and anyway, Mr. Feinstein had a better offer: Why not marry at Feinstein’s on the Upper East Side (otherwise known as his house)?

Because Mr. Postilio and Mr. Conlon already host a big annual party for their clients and friends, they chose an intimate wedding. On March 25, their parents and a few siblings gathered in the Champagne-hued, art-filled living room of Mr. Feinstein and his spouse, Terrence Flannery. Ms. Ebersole, a Universal Life Minister, officiated, with Mr. Feinstein at the piano.

But shortly into the ceremony, Mr. Postilio began to falter; Ms. Ebersole seated the couple on a tufted banquette, where Mr. Conlon rubbed his fiancé’s back protectively.

Mr. Postilio was having a panic attack. It had happened only a few times before, at other momentous occasions in his life, he said later. In the tumult of organizing the event, he hadn’t quite registered its emotional impact. His brother, Chris Postilio, took him outside for some fresh air.

Mr. Feinstein understood fully. He and Mr. Flannery had been together for many years when they were wed, by Judge Judy Sheindlin and Gabriel Ferrer, in 2008. “I didn’t think it was a big deal, and the minute we got up there, it was the biggest deal in my life,” Mr. Feinstein said, adding that weddings can carry a different weight for gay couples. “Terrence and I both felt the nakedness of that, the joy of it, and experienced a level of depth that was a complete surprise.”

After a brief intermission, Mr. Postilio returned, the color back in his face. Smiling, he rejoined Mr. Conlon to a lighthearted chorus of “you’re not sick, you’re just in love,” from Mr. Feinstein. With some words “from the gospel, according to Kander and Ebb,” Ms. Ebersole completed the bond of Tom and Mickey: “How the world can change,” she began in a soft singsong, quoting from “Cabaret.”

“It can change like that, due to one little word — married.
See a palace rise, from a two room-flat, due to one little word — married.
And the old despair that was often there, suddenly ceases to be.
For you wake one day, look around and say, somebody wonderful married me.”

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