The teenager branded the actor as void of ‘consideration or empathy’ towards his youngest children, before writing: ‘You will never understand the damage you have done to my family,’ sarcastically signing off the message: ‘So Happy Father’s Day, you f*****g awful human being.’

As the post goes viral, MailOnline takes a look into Pax Thien’s history and his fractured relationship with his father Brad…

Fuming: Pax labelled his father a ‘world class a**hole’ via his private Instagram story on Father’s Day 2020 (pictured: Angelina Jolie and Pax in 2018)

Hell: Pax Jolie-Pitt, 19, alleged Brad Pitt of making his life ‘hell’ in a fiery social media rant in 2020

Who is Pax Jolie?

Pax Thien Jolie-Pitt was born on November 29, 2003 in Pham Quang Sang, Vietnam.

His biological mother – who was battling addiction – abandoned him when he was only two days old  after discovering he had a liver problems.

He was later placed at the Tam Binh Orphanage in Ho Chi Minh City.

Later in 2007, Pax became the fourth Jolie-Pitt child at the age of three, after being adopted by Angelina Jolie.

He was named Pax Thien because it means ‘peaceful sky’, with Pax being the Latin word for peace and Thien meaning sky in Vietnamese.

After bringing Pax back to the USA, Jolie revealed to People Pax was getting used to his new found freedom.

She added he was  a ‘tough, remarkable little person.’

Jolie adopted the boy solo due to Vietnamese laws that make it difficult for unmarried couples to adopt.

She said: ‘He spent 3 1/2 years of his life in one place, in one room, in this one little iron bed with 20 other kids, and having no choice for himself to do things, having no freedom.

‘And suddenly, here he is in a very free situation with new brothers and sisters and a mom and dad.

‘He’s learning English and he’s so loving and he’s wild and free ’cause he suddenly has freedom so he’s a little wild and crazy.’

Not so happy Father’s Day: Pax and dad Brad in 2014 before the Hollywood actor’s divorce  with Jolie. Pax signed off his message: ‘So, Happy Father’s Day, you f***ing awful human’

Father figure: Brad Pitt formally adopted Pax in 2008 (Pictured: Angelina Jolie and Brad Pitt in 2006)

The child was later formally adopted by Brad Pitt in 2008, according to The Mirror.

Jolie shared Pax and Maddox both share a close bond, prior to the family making a visit to Vietnam before his eight birthday in 2011.

Pax has five siblings, Maddox Chivan, Zahara Marley, Shiloh Nouvel, Knox Leon and Vivienne Marcheline.

What does Pax Jolie Pitt do?

Pax graduated from a prestigious LA private school in 2021, but opted not to go as he did not want to make a ‘circus’ of the event, according to The Sun.

Earlier this year, Pax reportedly become an artist – creating work under the pseudonym ‘Embtto’ – however the Page Six story turned out to be a hoax.

The Jolie-Pitt child seemingly keeps a great deal of his personal life out of the public eye.

However, this has not stopped the 19-year-old from stepping into the movie world, voicing the character of  Yoo on Kung Fu Panda 3, as well as being a set photographer on Jolie’s film – First They Killed My Father in August 2022.

Detailing working with Pax and Maddox on various film sets, Jolie told People: ‘We work well together.

‘When a film crew is at its best, it feels like a big family, so it felt natural.’

Behind the scenes; Pax, 19, voiced the character of Yoo on Kung Fu Panda 3, and has also been a set photographer on Jolie’s film First They Killed My Father in August 2022 (Pictured in 2023)

What is his relationship with Brad Pitt like?

It is not clear whether Pax Thien and his father, Brad have a relationship as of late.

In 2020, it was reported Pitt was still estranged from his eldest son Maddox and Pax.

Maddox and Pitt have had a difficult relationship since a rumoured altercation on a private flight in 2016.

The Oscar winner was later acquitted of wrongdoing.

An insider told UsWeekly the Hollywood actor’s relationship with Maddox was ‘nonexistent’ and claimed Brad was not speaking with Pax, 19, either.

Another source told the publication in October 2019, the actor was hopeful about mending fences with Pax, as Maddox was studying abroad at Yonsei University.

They said: ‘With Maddox overseas [for college], Brad is also hopeful that Pax will also be interested in reconnecting without the influence of his older brother.’

Estranged: As of 2020 Pax was allegedly not in contact with his actor father

We are family! Pax has five siblings (Pictured: Pax, Shiloh Nouvel Jolie-Pitt, Vivienne Marcheline Jolie-Pitt,Angelina Jolie, Zahara Marley Jolie-Pitt, and Knox Leon Jolie-Pitt in 2019)