Who expected the Jonas Brothers to be part of the Final Four festivities? Who even knew the Jo Bros were back together?

Clearly, the 8,000 screaming, bouncing, boy-band fans who packed the Armory in Minneapolis on Saturday night for the Jonas Brothers’ first big show since, like, 2013.

If you’re not a young women between, say, 17 and 27, you probably don’t know that not only are the Jo Bros back together but just last month they scored their first No. 1 song ever, “Sucker.” They’ve released another new tune, with a documentary film on the way and a full-blown arena tour expected. The trio played three recent abbreviated club shows before Saturday’s high-profile comeback.

“How many of you came to our shows back in the day?” Joe Jonas asked, and about one-third of the crowd responded. The focus group continued giving the first-timers a chance to be recognized. And then Nick Jonas asked, “How many of you are seeing us for the first time having adult beverages? Cheers! Drink responsibly.” And then he sipped from his red Solo cup.

Yes, the Jonas Brothers are now adults: Nick, 26, just got married to a former Miss World-turned-actress; Joe, 29, is engaged to a “Game of Thrones” star, and Kevin, 31, is long married with two children.

The fact that the Jonases have matured into adulthood seemed to be part of the problem with Saturday’s 75-minute crowd-pleasing, no-encore show. The music was mostly exuberant teen pop-rock, which was just fine when the three brothers were Disney Channel darlings. Not sure if their fans were missing the Jo Bros just yet, especially since Nick has had an encouraging solo career and Joe hit the Top 10 with his group DNCE.

In fact, DNCE’s dance-pop “Cake by the Ocean” made a big splash on Saturday, with the crowd singing and dancing along as Joe strutted down the Armory runway. And Nick’s solo smash, “Jealous,” was a big winner, too, a slice of Princely falsetto soul, that was more mature — and sexier — than any of the trio’s bubblegum hits. And, in a show of brotherly love, Joe and Nick each got to sing a verse on the other’s hit.

Even though the crowd joyously sang along to everyone of the oldies, the Jonases need to move on for their own sanity. Sure, they seemed glad to be back. Heck, Kevin even went bouncing and spinning down the runway, and Joe pogoed and carried on like the rock star he always threatened to be in the Jo Bros heyday. Nick, per usual, just played his guitar and sang, seemingly concentrating more on music than performance.

When it came to old material, the siblings, backed by a relentless quintet and two singers, leaned on some of their more rocking, harder-edged tunes like the opening “Burnin’ Up” and “That’s the Way We Roll,” along with a taste of the power pop of “Hold On” and the balladry of “When You Look Me in the Eyes,” which sounds like it should be a country hit for some Nashville crooner.

A nice change of pace was “Love Bug,” the Jason Mraz-like ditty with just the three brothers singing accompanied by Nick’s guitar. The band didn’t join in until the bridge and then revved up for the ending, building to Joe’s big held note. That and his Billie Joe Armstrong-like punkish delivery on “Hold On” were his finest vocal moments.

The trio introduced two new numbers that suggest new directions: “Cool,” a breezy stroll with a Miami Beach vibe that was noteworthy only because the University of Minnesota cheerleaders, danceline and marching band joined in, and “Sucker,” the closing number with an au courant dance-pop vibe a la Maroon 5.

If nothing else, Saturday’s comeback show proved that boy-band pop is timeless with the crowd it first connected with. Still, it remains to be seen if the Jonas Brothers will have the same kind of second act that New Kids on the Block and Backstreet Boys, their great boy-band predecessors, have experienced.

Opening the concert was “Ex’s and Oh’s” hitmaker Elle King, whose sense of self was as strong as her blues-rock voice.