Taylor Swift, Justin Beiber and singer Selena Gomez will reportedly be sitting together at the Billboard Music Awards. Credit: Kevin Mazur/ Getty Images

Taylor Swift will play an unusual role at the Billboard Awards in Las Vegas this Sunday, May 19: Third wheel and/or referee to close pal Selena Gomez and on-and-off boyfriend Justin Bieber! A source tells Us Weekly that the singer-songwriter, 23, will sit in the front row at the MGM Grand Garden Arena right next to BFF Gomez, 20, who in turn will sit alongside Bieber, 19.

Gomez and Bieber have reunited more than once since their breakup back in January, and it's "clearly no accident" that they'll be seatmates at Sunday's high-profile awards show, the source says. "Their camps must have requested this seating arrangement," adds the insider. "No way would it have happened without their go-ahead."

As for currently single Swift? "Of course Selena's BFF will be sitting next to her!" the source adds.

Bieber was spotted rehearsing for the big show on Friday. "There was no sign of Selena, but he was in great spirits," an onlooker says of the performance, in which he'll croon "Take You."

After kissing backstage in Norway, the volatile couple were photographed cuddling in an Instagram photo posted by Bieber himself in late April. But during a May 10 radio interview, Gomez told the DJ that she's "available."

The Billboard Awards air live from Las Vegas on Sunday, May 18, at 8 p.m. on ABC.