The plot continues to thicken in the ongoing divorce battle between publishing scion James B. Fairchild and socialite Whitney St. John.

Page Six exclusively reported that Fairchild’s neuropsychologist girlfriend, Dr. Christine Borelli, recently filed a police report accusing St. John of following her, videotaping her, staring her down and making inappropriate comments at their children’s school assemblies.

Now we’ve learned that Fairchild also filed a police report back in 2012, accusing someone of breaking into his personal computer and accessing real-estate transactions, e-mails and banking and hedge-fund data.

The report alleges, “A suspect . . . did enter his computer without permission and did copy and download the hard drive onto an external hard drive.” It says the incident occurred in 2011, but Fairchild didn’t pursue it at the time “as he did not want to have the suspect charged.” The report was filed in Southampton, and police declined to comment on any investigation.

But multiple sources said the person Fairchild suspected was not his estranged wife St. John, but another member of her family.

The various police reports could become part of the divorce proceedings. “In a custody proceeding, everything is on the table,” said a source.

Fairchild and St. John have been in a divorce battle since 2011. They were back in court on Monday, and a trial is set for Oct. 15.

St. John’s rep, Donald Shlimbaum, said of the computer police report, “Mr. Fairchild has a fertile imagination.” He added of the report against St. John, “Anybody can make a police report about anything and anybody. If Ms. St. John was taping at her school, it was of her children.” Fairchild’s rep, matrimonial lawyer Michael Stutman, said, “Given what I know about the history of this case, it would not surprise me if there was involvement by other people.”

Fairchild and Borelli were seen Thursday at a Hamptons jewelry exhibit at Kitty Clay with their kids, where Fairchild bought her a pearl-and-diamond lariat by Sintessi’s Michel Piranesi.