Jennifer Aniston reached out to the actor after his son's Instagram post

Pitt's 19-year-old son Pax went on a rant on Father's Day about how awful his father was.

He wrote: "Happy Father’s Day to this world-class a***hole. You time and time and again prove yourself to be a terrible and despicable person."

"You have no consideration or empathy toward your four youngest children who tremble in fear when in your presence," he continued.

He added, "You have made the lives of those closest to me a constant hell. You may tell yourself and the world whatever you want, but the truth will come to light someday.

"So, Happy Father’s Day, you f***ing awful human being!!!" he concluded.

Pitt is reportedly reeling following his son's public post, but Jennifer Aniston is supporting him through it.

A source told OK! that she was worried about her former partner.

"Jen was hugely concerned for Brad and she reached out to him immediately," a source said.

"Her first thought was how upset he must be. To be attacked in that way by someone he cares about so dearly will have been heartbreaking for him," they added.

Aniston and Pitt have remained friends following their divorce in 2007.

The insider said Aniston has been a major support to Pitt in the years after their break-up.

"A lot of people assume they don’t talk as their break-up was so fraught, but they have been in touch for years and she has always been a rock of support," they said.

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