This is one duet to be jealous of.
Taylor Swift welcomed old pal Nick Jonas onstage during her second concert at New Jersey's MetLife Stadium Saturday to perform a special collaboration of his hit song "Jealous."
Before Swift, 25, revealed her surprise guest, she teased the crowd that he was a Jersey native and someone she has known since he was just 15-year-old.
Nick, 22, also happens to be the younger brother of Swift's former boyfriend Joe Jonas.
In fact, the "Bad Blood" singer's ex was in the crowd with his girlfriend and one of Swift's BFFs Gigi Hadid.

Taylor Swift and Nick Jonas perform onstage during 'The 1989 World Tour' live at MetLife Stadium on July 11.

Candice Swanepoel, Lily Aldridge, Taylor Swift, Uzo Aduba, Karlie Kloss, Behati Prinsloo and Gigi Hadid were welcomed onstage by Swift during the performance.

Taylor Swift performing onstage during 'The 1989 World Tour' at MetLife Stadium in East Rutherford, New Jersey.
"Joe and Gigi walked in moments before the lights went out for Taylor and were escorted to a VIP area," an eyewitness told the Daily News.
While Joe didn't share any pics of the show, he did give fans a glimpse from a tour he took of the New York Giants locker room while at the stadium to see Swift.
รขHey Mr. Manning ...," he captioned a pic of Giants quarterback Eli Manning's locker.
The star power at Swift's concert didn't stop with the Jonas', the blond beauty also brought Hadid out onstage along with models Candice Swanepoel, Lily Aldridge, Karlie Kloss, Behati Prinsloo and "Orange is the New Black" actress Uzo Aduba.

Joe Jonas shared a photo of Giants quarterback Eli Manning's locker at MetLife Stadium Saturday.
During Friday's performance at the venue, she surprised the audience with the U.S. Women's Soccer Team, Heidi Klum, Lena Dunham and Hailee Steinfeld.
Next stop on the "1989" tour is Washington, D.C. Monday.
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