"Honey, do you have to use the bathroom before you go on stage?"

At a Dillard's department store in Houston, Michele Mahone, a slim, youthful 43-year-old single mom, is tending to her only child, pop singer and online phenom Austin Mahone. Austin is one month shy of his 17th birthday, and on this breezy March afternoon, he's about to do something he's done with increasing frequency over the past year or so: meet and greet a throng of tween girls. Today, approximately 1,000 "Mahomies," as his genus of fan is known, have overrun the department store's first floor, where, in exchange for purchasing $100 worth of Trukfit clothing (Austin serves as the "youth ambassador" for Lil Wayne's clothing line), they can get a photo with the singer and, crucially, a hug. Never mind that the clothes are 100 percent bro, the crowd is 99 percent female—there are enough girls who've plunked down their monthly allowance to keep Austin grinning and hugging for the better part of an afternoon.

In a makeshift upstairs dressing room, Michele lays out Austin's freshly steam-ironed Trukfit ensemble while he quietly jokes with his live-in bodyguard-assistant and huddles with his management about tomorrow's big stadium gig with Demi Lovato, part of the annual Houston Livestock Show and Rodeo. Unlike his spirit animal, Justin Bieber, with whom he shares an origin story and a swoopy hairdo, Austin doesn't radiate obvious star power or ambition. He's a little mumbly, monotone; he doesn't readily make eye contact. He is, in other words, a teenage boy, albeit one who just might be on the verge of global pop superstardom.

Before slipping on his T-shirt and hoodie, Austin steals a moment in front of a full-length mirror and poses, shirtless. It's as much curiosity as vanity: He's been working out with a trainer for the first time, readying himself for impending celebrity (not to mention dating), and he's never had muscles before. "He's proud of himself," Michele says. Late one night a few weeks back, Austin couldn't sleep. As he often does, he picked up his phone and reached out to his fans, in this case posting a shirtless selfie to Instagram. Within an hour, the pic had 20,000 likes. Michele, who co-manages Austin, made him take it down, right now, young man. "As a mom, I can't help but worry about what other moms would think when their daughters saw that picture," she explains. "Austin's fans are so young." Austin, who attends Catholic church most every Sunday with Michele, didn't argue with her. "I get it," he says. "My fans are, like, from 2 to 21. I definitely want to please the parents."

At Dillard's, the only 21-year-olds in sight are sales clerks; the sea of girls lofting rhinestone-encased cell phones and homemade posters—MAHOMIE 4 LIFE!; ANGELA: FAN SINCE 2011!; GO TO PROM WITH ME!!!—are squarely middle-school and younger. As Austin primps upstairs, they sing along to the DJ's repeated spins of Austin's third single, "Say You're Just a Friend," a perky, Bieberesque, puppy-love twist on Biz Markie's horndog classic. Despite the backing of the major label Republic Records, which signed Austin to a reported seven-figure deal in August, the song hasn't made much of an impact on the radio—it's too wholesome, like a stick of kale-flavored bubble gum. "It's mushy," Austin admits.

Try as it might, "Say You're Just a Friend" is no "Baby." Not that Austin necessarily wants it to be: He finds Bieber comparisons both gratifying and frustrating. "Justin's inspirational," he says, "and it's flattering to be compared to him. It's cool. But I don't want people to see me as a copy of Justin Bieber. Sometimes I can't breathe without being compared to him. If I wear a certain hat: Justin Bieber. Wear a certain shirt: Justin Bieber. It's so annoying." Fortunately for Austin, Bieber doesn't seem to wear shirts in public anymore, just one indication—along with weed busts, canceled concerts, Holocaust trivialization, and hair unrest—of his headlong rush away from child stardom. Suddenly, there exists a vacuum in the hearts of tweens. Austin and his team mean to fill it.

Girls love Austin Mahone for a variety of reasons—"His voice his songs his eyes his hair his nose his smile . . . " says one representative 13-year-old without breath—but the unspoken reason they love Austin is this: He is theirs. Like nearly all the devoted Mahomies here, Maddie, 14, discovered Austin on YouTube, where his bedroom covers of Top 40 hits—beginning in January 2011 with Jesse McCartney's "Beautiful Soul," then moving on to the likes of Bieber, Bruno Mars, Chris Brown, Drake, Ne-Yo, and Adele—drew hundreds, then thousands, then millions of views. "I would go on the iTunes chart and see the hottest songs, then I'd cover them," Austin says. "People would go on YouTube and search for those songs. That's how I got my views. I'd post two or three songs a week."