McGregor, 46, Mavrakis, 51, called it quits on their 22-year marriage in May, an unnamed “family source” told the magazine.
They have four daughters raging in age from 6 to 21.
Winstead, 32,announced her splitfrom husband Riley Stears in May.
The People report emerged after photos of McGregor and Winstead kissing at a London cafewere publishedover the weekend.
McGregor, who played a younger Obi-Wan Kenobi in the “Star Wars” prequels, and Winsteadboth joined “Fargo”in its third season this year and play lovers on the FX series.
Reps for McGregor and Winstead didn’t immediately respond to HuffPost’s requests for comment.
This article originally appeared on HuffPost.