The children of veteran radio personality and notable voice actor Casey Kasem are speaking out publicly, claiming their step-mother, Jean Kasem, has restricted them from seeing their ailing father for the last three months.

"My father has advanced Parkinson's to the point that he is unable to voice his opinions," one of the children told ABC News, speaking on behalf of all three siblings. "For a man who made a living with his voice, we now have to be his voice. We are here to say, 'Jean, let our dad see his loved ones!'"

Kasem's three children, along with his brother and friends, held a protest at the Kasem estate in Holmby Hills, Calif., on Tuesday. They even shot their own footage of the protest to spread the word, holding signs that read "Casey, we are your voice now."

Kerri Kasem, one of the radio personality's three children from his first marriage, told ABC affiliate ABC7 that Jean Kasem won't answer their phone calls and tells them to go away when they show up at her door.

"We were children when they were married and she never accepted us," one of the children told ABC News. "As children, what could we do wrong? She was never welcoming to my dad's brother, my dad's mom either, but we tried to embrace her. We don't know why she is not letting us see him."

ABC News placed multiple phone calls to Jean, who played "Loretta Tortelli" on the television sitcom "Cheers," but her mailbox was full and she could not be reached for comment.

Casey Kasem, 81, had been seeing his children once a week up until three months ago, his children said. However, he would only be able to visit them at one of his children's homes, in line with his wife's wishes, his children said.

"We were more than willing to go his house but we were never invited there. And the problem is, his condition is advancing and all we want is to see him, and we want nothing else from her," one of his children said. "Our hope is that we band together and get a good outcome. The ideal situation would be to get visitation with my dad. He lights up when he sees his kids and his grandkids. We just want to be able to care for him during this time and give him a hug and put a smile on his face."

Longtime Kasem manager Don Pitts told ABC News that he "never gets involved" in family matters, and did not have additional information in regard to Kasem's current state and the public feud between his children and his wife.

The children said the feud is not about money, since they are independently wealthy, but about their "father's wellbeing."

"We don't want to see him go and not say goodbye and not love him and not support him. We don't know how long he has," Kerri said in her interview with KABC7.

Kasem, who also has a daughter with Jean, is widely known for being the host of the syndicated American Top 40 countdown show, which he ended with his signature sign-off, "Keep your feet on the ground and keep reaching for the stars."

He is also famous for voicing the character Shaggy in the Saturday morning cartoon franchise Scooby-Doo.

Casey Kasem is seen with is family in this undated photo. (Courtesy of the Kasem family)