Thomas Markle, the father of Meghan, Duchess of Sussex, could end up testifying against her in court, According to CNN, the potential legal battle would center around her treatment in the UK media.
Markle filed suit last year against the Mail on Sunday newspaper for allegedly unlawfully publishing a letter she wrote to her father.
The Mail on Sunday and parent company Associated Newspapers argue that there was "huge and legitimate" public interest.
It's not yet clear whether Markle will testify, should the case reach court.
Legal documents appear to show Meghan's father has been co-operating with the defense, making him a likely witness.
The Mail on Sunday told CNN that it would not make any official comment.