Sumner Redstone's granddaughter backs mental competency lawsuit

LOS ANGELES (Reuters) - A granddaughter of Sumner Redstone wants to join Redstone’s ex-girlfriend in a lawsuit challenging Redstone’s mental competency, court filings show, an indication the media mogul’s family is not united in its view of his condition.

Sumner Redstone (C), executive chairman of CBS Corp. and Viacom, is assisted as he arrives at the premiere of "The Guilt Trip" starring Barbra Streisand and Seth Rogen in Los Angeles in this December 11, 2012, file photo. REUTERS/Fred Prouser/Files

Keryn Redstone, in a declaration filed in Los Angeles Superior Court on Tuesday, said her grandfather became a “prisoner in his own home” after the former girlfriend, Manuela Herzer, was ejected from his mansion last October.

Herzer is challenging her removal last year as Sumner Redstone’s healthcare agent, saying the 92-year-old was not mentally competent to make that decision. Keryn Redstone asked the court to include her name on the petition, alongside Herzer’s. The case is scheduled to go to trial on May 6.

Redstone controls a majority of the voting stock at Viacom and CBS, and shareholders have closely followed the case for what it could reveal about his mental condition. The appearance of one of Redstone’s family members as a witness could lend Herzer’s allegations more credibility at trial.

Representatives for Redstone declined to comment.

In her court filing, Keryn Redstone also described a “troubled” relationship between her grandfather and his daughter, Shari Redstone, who is in line to be a key decision maker over the fate of Viacom and CBS after the ailing Redstone dies.

When Redstone was hospitalized in 2014, Keryn Redstone says, his daughter pushed for a “do not resuscitate” order over Redstone’s vehement objections. Herzer had made the same allegations in previous legal filings.

Keryn Redstone said Shari became angry when Keryn refused to change seats after Sumner Redstone asked her to sit next to him at his 91st birthday party so she could help him eat.

“Shari erupted and threatened to kill me,” Keryn Redstone said in the declaration.

A spokeswoman for Shari Redstone did not respond to a request for comment.

Keryn Redstone said she last saw her grandfather in February and “he just sat there, staring into space, unaware of my presence.” He has not responded to her entreaties to him since.

Keryn is the daughter of Sumner’s son Brent Redstone, who had a previous legal battle with his father. Brent Redstone filed a lawsuit in 2006 in a dispute over his share of the family fortune. It was settled out of court in 2007.

Additional reporting by Dan Levine in San Francisco; Editing by Bernard Orr