On a warm-for-March night, a foursome led by a 23-year-old fledgling fashion designer named Andrew Warren shimmied themselves into an Uber S.U.V. They were heading from a pajama-themed party at the Dolce & Gabbana store on Fifth Avenue to dinner at a new restaurant, Vandal, on the Bowery.

Dressed in a black corseted two-piece lent to her by Dolce & Gabbana, Kyra Kennedy, 20, handed her phone to the driver so he could plug it in for her. Ms. Kennedy is a daughter of Robert F. Kennedy Jr. Her porcelain-skin face was framed by a jeweled headpiece, which at the party had prompted Peter Brant Jr., a model, to remark: “Kiki! You look a bit like Josephine Baker.”

A few weeks later, Mr. Brant, 22, would be arrested at Kennedy Airport on charges of assault and disorderly conduct. Mr. Warren said of him: “Harry, his brother, is like my best friend. I know him from fashiony stuff from when we were younger. Not to take credit, but I kind of introduced them to everyone.”

Reya Benitez listened and laughed. Turning 24 at midnight, she wore a white slip dress designed by Mr. Warren, and bopped in her seat to the beat of Justin Bieber’s “Sorry,” asking the driver to turn the volume up, way up. “It’s my jam,” said Ms. Benitez, the daughter of Jellybean Benitez, a D.J. and music producer.

Sparkling in a see-through gold dress also on loan from Dolce & Gabbana was Gaia Matisse, the great-great-granddaughter of the painter Henri Matisse. “Andrew, do you have any pics?” she asked, turning to Mr. Warren.

“I need to look on my phone,” he said, the soft light of the screen bathing his face.

Las Vegas in the 1950s and ’60s had the Rat Pack. In Los Angeles in the ’80s there was the Brat Pack. Now, New York has become home base to a young, wealthy and itinerant group that one may think of as the Snap Pack. For them, taking photos and videos for Instagram and Snapchat is not a way to memorialize a night out. It’s the night’s main event.

In the S.U.V., the four passed their phones to one another, assessing the goods, texting pictures that they favored.

“Obviously I’m going to put a different filter on it,” said Ms. Matisse, 22 and raised in Paris and New York, as she considered whether to post a picture of herself and her friends.

Ms. Kennedy, a statuesque beauty, gazed at another photograph. “Oh my God, I look like a whale!” she said. She and Mr. Warren met about a year and a half ago. “He scooped me up in Aspen,” she said.

Often traveling together, the group members chronicle their lives tirelessly from beach to mountaintop to Mr. Warren’s parents’ apartment at the Majestic on Central Park West (to which he returned after graduating from Syracuse University in 2015) for their combined Instagram following of more than 100,000.

They have given one another goofy nicknames. Ms. Benitez is “the Chica,” the exact spelling of which is a point of contention among the friends. Ms. Matisse is “Koala,” Ms. Kennedy is “Hester.”

And Mr. Warren? “Have you seen ‘Willy Wonka and the Chocolate Factory’?” Ms. Kennedy asked. “He’s Veruca. ‘I want it! I want it! I want it!’”

Mr. Warren’s ambitions are at least in part driving all this social-media activity: He is trying to promote his new fashion line, Just Drew, so named after the breakup of a collaboration with a friend on a line of T-shirts.

He has since stepped up to more complicated garments. At a recent trunk show at the Shephard building in Greenwich Village, arranged with the help of a best friend who is a luxury real estate scion, he displayed navy blue palazzo pants ($295), silk wool blazers in both black and white with mesh netted panels in the back ($750) and signature handkerchief silk charmeuse slip dresses ($595), all made in the United States.

“I want my clothes to be realistic,” he said. “Sometimes people just do designs for attention, like they come out in a garbage bag.”

In a way, Mr. Warren, an only child, is just building on the family business. His paternal grandfather, David Warren, was a successful clothing manufacturer (his name is inscribed on the “Garment Worker” statue on Seventh Avenue, a man working at a sewing machine); he founded the Warren Group, which the family sold in 1998. Andrew Warren’s parents, Marcy and Michael Warren, worked in the company David founded, and are doing a lot of Andrew’s back-office work, as well as advising him. (They hired a seasoned designer to help execute their son’s vision.)

“We have a top that is in orange, and Andrew can’t stand it,” said Michael Warren, who is 60. “But I tell him, in Atlanta and Dallas they are going to love it, and you need to care about what they’ll love outside of New York.”

What Andrew Warren lacks in nuts-and-bold retail expertise, though, he makes up for with youth and app savvy. “The stores want him,” said Ms. Warren, 54. “They don’t want old moo-out-to-pasture me. They want the jack rabbit, they want the young blood. They want him and they want his friends.”

These includes Tiffany Trump, Donald Trump’s 22-year-old daughter with Marla Maples. With Ms. Kennedy, Ms. Benitez and Ms. Matisse, she modeled for Just Drew’s first New York Fashion Week show at Gotham Hall in February.

Among his older supporters is Jason Binn, 48, the magazine impresario who was a founder of Gotham, Hamptons and Ocean Drive, the latter started in part with money invested by Michael and Marcy Warren. Last summer, DuJour, another of Mr. Binn’s magazines, featured Mr. Warren and his set in a sprawling article called, “The (Real) Rich Kids of Instagram,” a reference to a website that mockingly aggregates lavish photos posted by the young jet set.

“Andrew’s a heavyweight, and it’s a very crowded field,” Mr. Binn said at the Dolce & Gabbana party.

Field of what?

“Everything!” Mr. Binn said. “He hustled and hustled, and he became friends with everyone and then best friends with everyone. He built a great Rolodex, and the next thing you know, he’s got them to work for him!”

Mr. Warren’s Rolodex is burnished, of course, by his agile Snapchat, which Mr. Binn called “more colorful than a Puff Daddy video.”

These seconds-long snippets take viewers to loud, throbbing nightclubs, show the gang smoking on balconies and posing near private jets. A recent scene focused on Lita, the Warren family’s live-in nanny and housekeeper, as she tried to step over doorway gates in place to limit the wandering of the family’s dogs as she carried a stack of empty pizza boxes.

“We’re at the Hampton Classic, get over that one!” Mr. Warren can be heard saying as he trained his camera on her.

Despite such displays, the “Rich Kids of Instagram” moniker rankles Mr. Warren and his clique. “I party and I have fun, but I’m doing something serious,” he said. “Like Rihanna, because she sings, and rappers — no one is judging them for going out. But when I go out it’s like a judge.”

Even as they grasp that their postings can draw scorn, the Snap Pack seems unable to relinquish the habit of social media, and the illusion of image control it affords. “I look good in pictures I take of myself,” Ms. Matisse said as the group settled in for dinner at Vandal.

Ms. Matisse, who said she is a method actor — “it’s my passion” — graduated in 2015 from New York University, where she studied “the self and other identities,” she said, “the Eastern psychology of ourselves and Buddhism and how the East is so much different from the West and it’s all very interconnected.”

She admitted some ambivalence about her activities on Instagram. “It’s so consuming, it takes so much time,” she said. “I hate the process of the Instagram, the contrast, the saturation, the filter,” she said of editing the pictures. “Then I send it out into the world and may not even ever see it again.”

Friends joined the table, seating arrangements were shuffled, and a bottle of eye drops was passed around, enhancing more sultry selfies. Barron Hilton, 26, brother of Paris, was among the stragglers from the Dolce & Gabbana party. He was wearing a bathrobe and chatting excitedly about his Instagram food blog, Barron’s Bites. The waitress carded the diners as they ordered cocktails. Mr. Warren got an extra glass, and several of the friends poured in their drinks: straight vodka, margaritas, something and tonic.

Ms. Kennedy sipped the concoction with a straw and smiled sweetly as a photographer captured the moment. “Sorry, Dad!” she said with a laugh.

A week later, the Snap Packers gathered early on a Tuesday morning in the green room of “Good Day New York,” the local Fox morning news and talk show, for a segment focusing on Just Drew. Mr. Warren’s mother is a friend of one of the hosts, Rosanna Scotto. Mr. Warren would be interviewed as Ms. Kennedy, Ms. Matisse and Ms. Benitez modeled.

Also serving as a model was Alexa Greenfield, 23, another friend of Mr. Warren’s and an entrepreneur whose ventures include jewelry for men’s ties. “I’m friends with Andrew, but I’m tamer,” Ms. Greenfield said. “I’m hidden, I don’t let him put me on Instagram.”

She chatted with Blake Frank, a Just Drew employee, and Chris Bolos, who does production, sourcing and other tasks for the family.

Ms. Matisse was not there yet. She had slept at the Warrens’ apartment and was apparently concerned about leaving her teacup longhaired Chihuahua there. “Marcy has three dogs,” Mr. Bolos said, “and Gaia has a little rat.”

Perhaps she could just bring the dog to the Fox studio, someone suggested.

“We’ve had segments on wild animals before,” a Fox publicist said.

“They’re animals all right,” Mr. Bolos said dryly, referring to the Snap Packers.

Late to arrive were Mr. Warren, Ms. Kennedy, Ms. Matisse and Bambi, her dog, which was dressed in a monogrammed cashmere sweater. Social media happens on their schedule; old media less so. Mr. Warren had to drag his friends out of bed. “I feel like I’m a parent getting a kid up for school,” he said.

Though the stakes were low — the Just Drew line is, for now, mostly available on the company’s website — Mr. Warren was nervous, sitting on a chair in skinny black jeans with frayed leather patches and a fitted T-shirt (having lost 88 pounds a few years ago, he takes pride in his physique).

Mr. Warren remarked on Ms. Trump’s absence. “With Tiffany Trump, there is too much going on,” he said. “It was great press, but it was a distraction from the designs. I don’t want to mix with politics.”

He has done charity work, however, including starting the first junior committee for Denise Rich’s cancer foundation when he was in eighth grade. “I got Natasha Bedingfield and the cast of ‘Gossip Girl’ at the first event,” he said.

Dressed in Just Drew pants and a crop top, Ms. Benitez sat with her phone looking at photos of herself in Miami, then sat on the arm of Mr. Warren’s chair and began snapping the two of them. He nudged her away. “He doesn’t love me anymore,” she said, fake pouting.

“I like to take photos,” he said, “but I’m not a bad person. I’ve had a cancer patient D.M. me on Instagram and say, ‘Your Instagram snaps give me hope.’ She said I inspire her and I make her want to keep going every day so she can have a fun life.”

But then it was time for him to do a quick primp. Mr. Warren wears his hair in a comb-forward, and it requires certain maintenance.

“Fix the swoop,” Ms. Benitez advised him.

“I want to do it right before we go on because it falls immediately,” he said.

The time arrived, the swoop was swooped, and the group got ready to head to the set. But first, they posed for a group selfie.