Nick Jonas was left red-faced as Demi Lovato lifted the lid on his love life when they appeared on Carpool Karaoke with James Corden.
The US stars, who are about to embark on a tour together, insisted they were just friends and had never been romantically involved with each other.
But Demi, who once dated Nick's brother and former bandmate Joe, was quick to disclose details of Nick's past high-profile relationships with Miley Cyrus and Selena Gomez.
"I don't know if you've noticed but I kind of go for older guys - no offence," Demi said.
"It was Cyrus, Gomez, Cyrus, Gomez and then I don't know what else happened."
Nick responded: "Are we going to keep talking about my dating life?"
After belting out some of their own songs, the trio performed Cake By The Ocean by DNCE, featuring Nick's brother Joe.
"It's about sex," Nick said.
"Joe was writing the song with people from Sweden and they were like; 'What's that thing - like cake by the ocean.' He said; 'You mean sex on the beach?' That's how it was born."
The trio then jumped out of the car to form an impromptu street band, with James using buckets as drums, Nick on guitar and Demi on vocals.
With a Hollywood tour bus stopping to watch the new music group, they raked in handfuls of cash from the audience gathered.
Late Late Show presenter James joked: "I heard someone say; 'I normally hate those two, but with him it's amazing'."