The D’Auria-Gupta brothers have been in harmony for as long as they can remember but the 18-year-old fraternal triplets have already amassed a string of successes as a family singing act.

Carmine, Francesco and Marconi started practicing tunes as children about a decade ago, but grew into serious singers with performances at Carnegie Hall, Madison Square Garden and at the 2008 U.S. Open tennis tournament in Queens.

Over the past few years, they’ve performed classical pieces with the Metropolitan Youth Orchestra of New York and as a barbershop group with brothers Gaetano, 20, and Leonardo, 15.

“Since we’re all related, the way our voices blend and work together just gives it a different sound than when it’s just four unrelated people,” said Marconi, a tenor.

“We have a very similar timbre,” added Francesco, a bass, referring to the quality, or “color,” of a voice.

Barbershop songs have four parts, so when all five brothers sing together, two of them double up on a part.

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In October, the brothers sang Italy’s national anthem at a basketball game at Madison Square Garden between teams from Italy and Israel. They’ve performed at Carnegie Hall several times with the Metropolitan Youth Orchestra.

The D’Auria-Guptas grew up in Long Beach and Rockville Centre before moving to Locust Valley as middle schoolers.

Their father, Rom Gupta, is a gastroenterologist. Their mother, Maria D’Auria, plays piano and started them singing as young children, while they attended a now-closed private school founded by their parents in Long Beach called the Renaissance School.

They underwent classical training with a series of private teachers. After they entered Locust Valley schools in the seventh grade, they joined the school chorus and have performed in two high school musicals: “The Music Man” and “State Fair.”

“They just bring so much talent to the game,” said Bill Margiotta, the high school and middle school choral director in Locust Valley schools. “They make your job so easy. They’re so well-trained, and they share that freely with the other students,” he added. “Such great maturity, but they’re very kind people besides all that.”

Singing isn’t the only interest the triplets have in common. They each play varsity tennis, piano and a string instrument, and are also members of the robotics team.

But they all agree that music has a central place in their lives. Francesco said he’s motivated by the joy of hearing a piece come together.

“After you’ve learned the notes, then you go to put all the parts together as one, that’s the best part about it,” he said. “That’s the drive. After you’ve done the work of learning the notes, then, when you put the piece together and hear the harmonies, that’s when it’s really fun.”

Marconi said singing helped instill “the ability to be very hardworking, very motivated and be very dedicated to something.”

All three are headed to Stony Brook University in the fall. Carmine plans to study mechanical engineering. Francesco wants to study business. Marconi is leaning toward information systems and has joined the Army Reserve Officers’ Training Corps.

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The siblings said they may join the college’s chorus. They’ll commute to school freshman year, so if they feel like practicing, they need only go as far as home, or the car.

FRESHMAN FAST-FORWARD “It’s just doing everything by myself, exploring my individuality,” said Carmine. “It’s really interesting, because it is going to be a new thing for us. It’s something we never had.”

WHAT MAKES YOU EXTRAORDINARY: “Growing up, we had friends, but it wasn’t ever like an issue,” said Francesco. “It wasn’t like we had to have 10 or 20 friends, because if we were with each other, we were never really bored.”