Brad Pitt is fighting for joint custody of his children.

Brad Pitt and Angelina Jolie

Brad Pitt and Angelina Jolie

The 'By The Sea' star's estranged wife Angelina Jolie filed for divorce earlier this week and is seeking sole physical custody of their six children - Maddox, 15, Pax, 12, Zahara, 11, Shiloh, 10, and twins Knox and Vivienne, eight - but Brad intends to fight for equal rights.

The 52-year-old actor is set to respond to the divorce petition submitted by Angelina, which seeks to only give him visitation rights, TMZ reports.

The news comes only hours after it was revealed that Brad is reportedly being investigated by the FBI over claims he verbally and physically abused one of his children whilst drunk on a private jet.

A member of staff said previously: "There was a disagreement with the eldest boy. I know it started on the way to the airport before the plane took off and escalated on the plane.

"It was a teenage thing, there is a lot of hormones going on. They were gone for over 10 days. You put eight people in a little tube like that and put them up in the air for 12 and a half hours, add this and that to it."

Brad is said to be taking the investigation "very seriously" and is "scared" he will lose his children over something that never happened.

Another source added: "He takes the investigation very seriously and he is cooperating fully. He was not physical in the way that has been reported. He will always do whatever is best for his kids."

Whilst a member of staff shared: "I have never seen Brad like this. He is distraught, pacing, nervous - totally terrified. He is just expressing to me that he is scared. He is scared of losing his kids over something that he hasn't done and him being made out to look like a bad father. He is far from a bad father. He's not able to see the kids at the moment but he is constantly in touch with staff asking to make sure they're OK. He keeps saying, 'Just look after my kids, that's all that matters right now.'"