Jeff Bezos has been trying desperately to find out who leaked texts and images between him and his girlfriend to the Enquirer.
On Sunday, cited multiple unnamed sources as saying it was his girlfriend's brother, Michael Sanchez.
Business Insider says he obtained the couple's private text messages and passed them to The National Enquirer.
Michael Sanchez had previously emerged as a suspect in the leaks.
AMI, the tabloid's parent company, had hinted earlier Sunday that a "reliable" source close to the two people provided "information."
Bezos said the Enquirer had threatened to release more photos if he did not publicly walk back his suspicion that the leak was politically motivated.
Sachez is an outspoken supporter of Donald Trump. President Trump has slammed Bezos repeatedly during his term.