Singer Mariah Carey has added fuel to rumours that she's dating her longtime friend and film producer Brett Ratner, by being photographed during a vacation with him.

Carey and Ratner, who have been friends for years, reportedly grew closer since her split from her former husband Cannon in 2014.

`Their relationship has progressed in recent weeks and is now very serious. They're a hot couple,` an insider told RadarOnline.com.

`Carey and Ratner jetted off to St. Bart's on March 27 for a joint birthday getaway. Ratner's birthday is on March 28, and Carey's birthday, which she prefers to call her 'anniversary' is March 27,` the source revealed.

The couple left out of a private Los Angeles airport on Australian billionaire James Packer's private jet on Friday, said the source.

Once in the Caribbean, they were expected to stay on the $70 million super-yacht Ultima III. Featuring eight staterooms and a jacuzzi, the 190-foot boat has plenty of room to lounge.

Carey and Ratner recently went public on a dinner date with rocker Courtney Love at on March 24. Both posted a photograph of the night on image-sharing site Instagram.

Ratner captioned the image: `I love these ladies.`

Ratner has been the director of Carey's eight music videos including "Heartbreaker", "I Still Believe" and "We Belong Together."