Charlize Theron and Sean Penn have been dating for a while now, and while sources say they aren’t engaged just yet, they are set to collaborate in other ways; namely, on a film which Penn will direct and Theron will star in.

The movie, The Last Face, focuses on two philanthropic doctors–played by Theron and Javier Bardem–involved in humanitarian efforts in Africa. The two of them fall in love, but end up getting caught in the middle of political strife during the course of their work. Penn will not only direct, but will also fund and produce the film.

Both actors are heavily involved in humanitarian work–Penn hosts an annual Help Haiti Home gala, at which the duo came out as a couple in January–so the film will be a labor of love for both of them.

Speculation that Penn was courting Charlize began over the holidays, when they were spotted vacationing together in Oahu. Sources told People Magazine that the duo had been close friends for years.

“Charlize and Sean have been friends for years,” the source said. “They have been spotted out together several times in the past few years. Even when Charlize was dating Stuart [Townsend]. They both had dinner with Sean several times.”

The couple haven’t made things official–yet–but sources say it may not be long before we see Charlize with a diamond on her finger.

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