Diane Lane has been part of the DC Extended Universe since the beginning, debuting as Martha Kent in Man of Steel and returning last year in Batman v Superman: Dawn of Justice.
How exactly Martha fits into Justice League remains to be revealed, though she’ll be one of the many supporting characters from the heroes’ personal lives.
Later on, Martha was kidnapped by Lex Luthor, but saved by Batman before Anatoly Knyazev could kill her, and during Superman’s funeral, she gave Lois Lane the engagement ring that Clark planned to give her.
Warner Bros already has a number of DC movies in development (including Aquaman, which is currently shooting), but Justice League’s critical and commercial performance will definitely dictate how the franchise is handled in the years after.