A legal petition seeking to change the names of the children to Zahara Jolie-Pitt and Maddox Jolie-Pitt was filed Friday in Los Angeles, publicist Cindy Guagenti said in a written statement to The Associated Press.
"We are confirming that Brad Pitt is in the process of becoming the adoptive father of both children," the statement said. "No further comment is being made."
The couple has been romantically linked since the filming of "Mr. & Mrs. Smith."
For months, rumors have been circulating about the extent of Jolie's off-screen relationship with Pitt. Photos published in the July 11 issue of People show Jolie standing near her England estate while Pitt rides a dirt bike with Maddox, 4. Other photos show Pitt, Jolie and Maddox at Luton Airport outside London.
Both children were adopted by Jolie. Zahara is just under a year old.
Pitt and Jennifer Aniston announced their separation in January, and Aniston filed for divorce in March, citing irreconcilable differences. The divorce became final in October. Pitt, 41, has denied Jolie, 30, was the reason for the split.