The Hinduja family are among the world’s richest. The bulk of their fortune derives from Hinduja Group, the closely held conglomerate whose origins trace back more than a century that today has investments spanning finance, media and health care in almost 40 countries, according to its website. The Bloomberg Billionaires Index values the family fortune at $11.2 billion.

A letter signed by the four Hinduja brothers is at the center of a legal dispute over the future of the family’s $11.2 billion fortune. The 2015 document says that the assets held by one brother belong to all, and that each man will appoint the others as their executors. But now Srichand Hinduja, 84, the patriarch of the family, and his daughter, Vinoo, want the letter declared worthless.

The dispute between the U.K.-based family came to a light in a ruling delivered Thursday by a London judge, who said that the three other brothers, Gopichand, Prakash, and Ashok, used the letter to take control of Hinduja Bank—an asset that was in Srichand’s sole name.

Srichand and Vinoo want the court to rule that the letter should have “no legal effect” and cannot be used as a will, the judge said. She said that Srichand had insisted as early as 2016 that the July letter doesn’t reflect his wishes and that the family’s assets should be separated.

A lawyer for Srichand didn’t respond to messages seeking comment. An attorney for the three other brothers couldn’t immediately comment.

The three brothers said that if the claim succeeds then all assets in Srichand’s name would pass to his daughter and her immediate family, including the entire shareholding in Hinduja Bank, according to the ruling. The judge said that Srichand lacks capacity to give instructions to his lawyers and appointed Vinoo to act on his behalf.

The four Hinduja siblings now help to run the Mumbai-based group, which suffered in the economic turmoil stemming from the pandemic. Shares in Ashok Leyland Ltd., the Indian truck-maker controlled by Hinduja Group’s automotive unit, fell more than a third in March. The global slowdown in travel also hurt the group’s Gulf Oil International.

This month, India’s central bank pushed back on the brothers’ plan to raise their stake in IndusInd Bank Ltd., which has lost more than 70% of its market value this year, according to people familiar with the matter.