The pair have been dating since June, when they were spotted vacationing together in Capri, Italy.
A source recently told E! News about the couple, "They get along amazingly and their communication is always fluid and easy. James is very into Mariah, though, and he wants to spoil her and her children every minute he can. He feels she only deserves the best."
The insider added, "James has been speaking to his family and friends back in Australia a lot about Mariah. This is just the beginning of their relationship, and they are both excited about what possibly can be ahead for them in the future."
"Extra's" AJ Calloway was on the red carpet at the premiere catching up with Mariah and the movie's stars, Anne Hathaway and Robert DeNiro. Check out the video to see Anne freaking out as Mariah arrived to the premiere!