According to Radar Online, Mariah and Brett have grown closer since her split from Nick in 2014. An insider tells the site, "Their relationship has progressed in recent weeks and is now very serious. They're a hot couple."
The insider reveals the rumored couple jetted off to St. Barts on Australian billionaire James Packer's private jet on Friday, March 27 for a joint birthday. Mariah's birthday was on that day while Brett was on the next day. They reportedly stayed on the $70 million super-yacht, Ultima III, which features eight staterooms, a jacuzzi and plenty of rooms to lounge.
On Friday night, Mariah shared on Instagram a photo collage of her enjoying champagne and fireworks as she celebrated her birthday. "Happy 3/27 #lambily I [love] U and can't wait for this new year and all the excitement of 2015 Dahhhlings!!!" she captioned it.