Media mogul Rupert Murdoch has launched a secret legal battle against three of his children in a bid to preserve his empire’s conservative bent, according to court documents seen by The New York Times.

The Times reports that Murdoch wants to change the terms of an irrevocable family trust that currently hands control of the family business to his four eldest children.

A sealed document obtained by The Times shows the 93-year-old wants to ensure his eldest son Lachlan remains in charge of the Murdoch TV and newspaper empire after his death.

Lachlan is the more conservative of Murdoch’s adult children and his chosen successor.

The Times reports that Murdoch is seeking to ensure the empire he founded remains a conservative political force even after he dies.

The current legal move was reportedly set in motion last year.

According to The Times, Murdoch is arguing in court that empowering Lachlan to run the company without interference from his more politically moderate siblings will preserve its conservative editorial bent and protect its commercial value for all his heirs.

“Those three siblings — James, Elisabeth and Prudence — were caught completely off guard by their father’s effort to rewrite what was supposed to be an inviolable trust and have united to stop him,” The New York Times writes.

Lachlan has reportedly joined Murdoch’s side.

Last month, the Nevada probate commissioner found that Murdoch could amend the trust if he could show he was acting in good faith and for the sole benefit of his heirs, according to a copy of his 48-page decision.

A trial to determine whether Murdoch is acting in good faith is expected to start in September.

Representatives for the two sides declined to comment.

Murdoch stepped down as the head of his news media empire in September, replaced by Lachlan who has been described as “considerably more brutal” than his father.

“The time is right for me to take on different roles, knowing that we have truly talented teams and a passionate, principled leader in Lachlan who will become sole chairman of both companies,” Murdoch said in a memo announcing he was stepping away from his role as chairman of News Corp last year.

Lachlan has worked within his father’s businesses for decades, albeit with a few expeditions into other ventures, and is vastly familiar with the news business his father inherited from his grandfather in 1952.

Originally seen as the natural heir to the Fox News and News Corp empire, he left the company in 2005 after a feud with Fox News CEO Roger Ailes.

After nine years outside his father’s business, where he invested in media and marketing companies to middling success, the younger Murdoch returned as the prodigal son at a sensitive time, dominated by the News of the World phone hacking scandal.

In 2015, he was named co-chairman of 21st Century Fox with his brother, James, before the film studio was sold to Disney in 2019.

James quit, frustrated with News Corp’s climate change coverage, editorial content and strategic decisions, leaving Lachlan as the sole heir to his father’s treasured media holdings after being named chairman and CEO of Fox Corporation.