Documents show how bitter Angelina Jolie and Brad Pitt's custody battle has become

Angelina Jolie and Brad Pitt attend the EE British Academy Film Awards 2014 at The Royal Opera House on February 16, 2014 in London, England. Photo / Getty Images

Documents in the bitter custody battle between Brad Pitt and Angelina Jolie have reportedly revealed that three of their children wanted to testify against him.

Us Weekly reports that Jolie's lawyers filed documents in December claiming half of his children wanted to speak out against the Moneyball star.

Pitt, 57, shares six children with Jolie, 46, including Maddox, 19, Pax, 17, Zahara, 16, Shiloh, 15, and twins Knox and Vivienne, 12.

"The children whose custody is at issue are old enough to understand what is going on," the document obtained by Us Weekly reads. "The trial is necessarily going to impact them emotionally. Three of the children have asked to testify. To make any of the children endure what may be a futile and void proceeding is beyond unjustified. It is cruel."

Brad Pitt, Angelina Jolie and their six children Maddox, Pax, Zahara, Shiloh, Knox, and Vivienne arrive at Haneda International Airport in Tokyo, Japan. Photo / Getty Images

It is unknown which of Pitt's children were willing to give evidence to the court.

The document was filed as part of Jolie's ongoing attempt to have Judge John Ouderkerk removed from the case because of his alleged connections to Pitt's legal team.

Jolie says that Ouderkerk failed to disclose "ongoing business and professional relationships" with Pitt's lawyers.

Her request however was shut down and the judge remained on the case.

"Judge Ouderkirk denied Ms Jolie a fair trial, improperly excluding her evidence relevant to the children's health, safety, and welfare, evidence critical to making her case," the documents claimed.

Brad Pitt and Angelina Jolie visit The Field Museum with their children on August 11, 2007 in Chicago. Photo / Getty Images

Maddox, who is 19 and no longer a minor, did testify against his father in March.

"It wasn't very flattering toward Brad," a source told Us Weekly of the teen's testimony. "He doesn't use Pitt as his last name on documents that aren't legal and instead uses Jolie. Maddox wants to legally change his last name to Jolie, which Angelina has said she doesn't support."

Ouderkerk issued a tentative custody order in May giving the pair joint custody of the kids.

A source told Us Weekly at the time that the Eternals star was "bitterly disappointed".

Another hearing is scheduled for July 9.

Jolie's appeal will be heard by a three-justice panel.