According to Page Six, witnesses say the pair got cozy at a restaurant near the ArcLight movie theater in Los Angeles, the movie's premiere location, where they spent some time with a group of friends.
Pitt and Miller were "heavily enjoying each other's company," and "were talking to each other all night," a source told the publication.
Another insider added that Pitt, who's been caught looking frail in recent months, was "in very high spirits, which he hasn't been for a long time. He seems to be over a hump."
Miller previously denied dating rumors, saying: "So this is the truth about that: Brad Pitt is producing the movie that I just wrapped, but I didn't see him. He's not been to the set. You know, he's the producer of the film and I've met him twice. It's insane."
Meanwhile, sources say Jolie has banned her kids from calling their dad in recent weeks.
As for their recent rendezvous, reps for Pitt and Miller did not comment on the matter.
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