A granddaughter of Sumner Redstone is vowing to take legal action to support Viacom’s board of directors in the escalating fight between the mogul’s daughter and Viacom’s incumbent management for control of the company.

Keryn Redstone, a niece of Shari Redstone, has accused her aunt of executing a plan “to totally isolate and effectively kidnap, brainwash, and take advantage of my grandfather due to his debilitated state of mind and frail health.”

In a statement distributed by attorney Pierce O’Donnell, Keryn Redstone said she would soon take legal steps to “join with the Viacom directors in our common cause to liberate my grandfather from Shari’s clutches and protect my fellow trust beneficiaries and myself from her machinations.”

Keryn Redstone also reiterated her support for Manuela Herzer, Sumner Redstone’s one-time girlfriend who was removed from the mogul’s home last October at the instigation of Shari Redstone. Herzer filed a suit last year in an effort to restore her power over Sumner’s health care decisions, claiming that Sumner was mentally incapacitated and unable to make the decision to remove her from his life on his own.

In May,  a Los Angeles Superior Court judge dismissed Herzer’s action after the 93-year-old media baron indicated his dislike for Herzer in a videotaped deposition. Keryn Redstone had filed statements of support for Herzer’s position during the litigation although the judge prevented her from formally joining Herzer’s action.

O’Donnell represented Herzer in that suit and has filed a subsequent action on Herzer’s behalf against Shari Redstone. The new suit asserts that the younger Redstone violated Herzer’s privacy and interfered with Sumner Redstone’s plans to leave her substantial money and assets in his will.

Here is the full statement from Keryn Redstone:

I want to express my support for the Viacom directors who have tried to meet with my grandfather but have been denied access by Shari Redstone, not my grandfather. There is no way that a competent Sumner Redstone, acting of his own free will, would ever refuse to meet with his fellow directors who have been his close friends and allies and so loyal to him over many years.

Manuela Herzer and I have also been prevented by Shari from seeing my grandfather. We are two of the persons who were the most devoted to his welfare and protecting him.

Shari and her family have managed to totally isolate and effectively kidnap, brainwash, and take advantage of my grandfather due to his debilitated state of mind and frail health. They have lied to him about Manuela Herzer, the loyalty of his long-time friends like Philippe Dauman and George Abrams, and me. So far, Shari and her three adult children have succeeded in reversing decades of my grandfather’s careful estate planning and are poised to seize control of Viacom and CBS.

My grandfather (whom I affectionately call “Grumpy”) and I have had a very close and loving relationship ever since I was a little girl. Last September, when his health started rapidly failing, my grandfather and Manuela asked me to move into his house to help with his healthcare needs. Without hesitation, I moved from Colorado to Los Angeles.

Sadly, in mid-September, I noticed that my grandfather’s mental health was deteriorating. I witnessed with dismay his utter dependency on his nurses, especially Jeremy Jagiello. This made me very worried because my grandfather had never depended on anyone.

The grandfather whom I knew and loved so much was gone. He could barely communicate at all, and he was unable to appreciate and understand what was going on around him.

Manuela was the person closest to my grandfather in the world. Shari set Manuela up and had her ejected from my grandfather’s home last October when my grandfather was not able to communicate intelligibly or understand what was going on around him. Shari’s removal of Manuela from my grandfather’s life is a perfect example of her disregard for what is in his best interests.

With Manuela no longer there to protect my grandfather, Shari took charge of his health care and everything else in his life. I witnessed Shari yelling at him and treating him like a child. My grandfather sobbed uncontrollably, telling me over and over again, “I miss Manuela.” It was unbearable to watch him suffer so needlessly. I knew that I had to do something about this.

For as long as I can remember, my grandfather had done everything that he could possibly think of to prevent Shari from having any type of control or power over his companies, whether public or private. This was no secret to anyone. I can assure you that Shari is the last person on the planet to whom my grandfather would entrust his healthcare if he were of sound mind. I am therefore heartbroken and devastated to see this tragic turn of events in my grandfather’s life. Not to put words in his mouth, but what his happening now would be his worst nightmare if he had even the slightest mental capacity or understanding of what Shari was doing to him.

The last time that I saw my grandfather was on Valentine’s Day for fifteen minutes. As he sat there lifeless and flanked by his nurses and caretakers, he seemed unaware of his surroundings. It was one of the most surreal experiences of my life.

I quietly sobbed as I held his cold hand before they made me leave and never let me return, despite all my unanswered emails, text messages, and voice messages to his home, lawyers, personal secretary, and doctors as well as Shari. My experience is the same as the Viacom directors—Shari will not let us see Sumner. Because I was in the house, I know that my grandfather has been incompetent since last October. This is why Shari is keeping me away, because I will not lie or conceal the truth about my grandfather’s condition. I love my grandfather, and I cry myself to sleep every night knowing that I might never see him again.

I do not intend to let Shari get away with this outrage. I will soon be announcing legal steps to join with the Viacom directors in our common cause to liberate my grandfather from Shari’s clutches and protect my fellow trust beneficiaries and myself from her machinations.