Brad Pitt feels like he is drifting away from his kids the longer his custody battle with Angelina Jolie drags on.

The "Ad Astra" star has been embroiled in an ugly custody battle over their six kids since the actress filed for divorce in 2016. Jolie had suggested that the actor is not fit to take care of their children when she cited an alleged incident in 2016 that he hit their son Maddox while on a private plane.

The Los Angeles County Department of Children and Family Services has since then investigated Pitt and cleared him of child abuse allegations. However, when things seemed to be heading to the right path for the exes, the "Tomb Raider" actress filed another suit accusing him of spousal abuse.

Jolie filed the domestic violence complaint earlier this month and even put their children's names as witnesses. In the court documents, she wrote that their kids, Maddox, 19, Pax, 17, Zahara, 16, Shiloh, 14, and twins, Knox and Vivienne, 12, would be willing to provide "proof and authority" to her claims.

Pitt has since denied that he attacked her but Maddox's testimony is reportedly not in his father's favour. A source claimed that he testified as an adult in the ongoing custody battle and that "it wasn't very flattering toward Brad."

Pitt, on the other hand, reportedly acknowledges his "strained" relationship with his son and he is "heartbroken" about it. He knows that there is still "more work to be done" and "hasn't given up hope."

"Brad thought there was some real healing and progress done with Maddox," a source told InTouch Weekly adding that they are both still working through some issues together and that Pitt will always be there for his son and his siblings.

The 57-year old actor reportedly feels like he is "being more and more isolated from his children" and he is "devastated about it." The source claimed Pitt's "biggest regret in all of this is the fractured relationships he's had with all his children." He finds his relationship with Maddox "is the toughest" and "very challenging."

It is said that Pitt and Jolie's custody trial will end in April with Judge John W. Ouderkirk appointed to give the ruling. Their children reportedly gave testimonies to court-appointed therapists although it is yet to be proven if Maddox's negative testimony about his dad is true.

Angelina Jolie and Brad Pitt
In photo: (Left to Right) Angelina Jolie, son Maddox and Brad Pitt Robyn Beck/Getty