Kerri, 41, and a growing number of Kasem's loved ones, point the finger at Kasem's second wife, Jean.
Kasem, 81, the legendary host of radio countdown show American Top 40, has advanced Parkinson's disease, and his family and friends – including his other daughter Julie, 38; his son Mike, 40; his younger brother Mouner, 77 – say he's been cut off from the outside world by his wife of more than three decades.
"Keeping us from our father is the worst thing she could possibly do for his health," says Kerri, a host on Clear Channel radio, who adds their relationship with Jean, 59, has been estranged their whole lives.
"When he was healthy, our dad used to talk to us all the time. We're his joy. He began having trouble speaking about three years ago. Now we've been cut off from him. The same goes for many of his friends. We just want to know that our dad is okay."
In an unusual scene Tuesday, more than a dozen of Kasem's closest friends held signs outside the ornate wrought-iron gates of his 2.4-acre estate, demanding that Jean allow them access to Kasem, who, multiple family sources say, is ailing and cannot walk unassisted. He began showing symptoms of Parkinson's about seven years ago, according to his daughters. He was formally diagnosed shortly thereafter.
Blocked Access"In the past 30 years my brother has been married to Jean, I've only received one return phone call from her and I'm only able to see him at occasional events," his brother Mouner tells PEOPLE. "She's blocked access to my brother, but I've never questioned him about his marriage."
Adds Don Bustany, 85, who co-created American Top 40 and has known Kasem since they were teenagers: "This situation is outrageous. Jean has not allowed him to see his children."
Multiple attempts to reach Jean, an actress best known for her role in the short-lived Cheers spinoff in the '80s, The Tortellis, were unsuccessful. A lawyer who represents her in an unrelated civil case didn't immediately return a message seeking comment.
The activist couple, who have one daughter together, Liberty, now 23, have been known to throw their support behind social justice issues, including homeless rights, muscular dystrophy awareness and animal rights.
Kasem, a Detroit native and son of Lebanese Druze parents, launched his popular radio show in 1970 (having passed the baton to Ryan Seacrest in 2004) and provided voiceovers for thousands of commercials and TV shows, most famously for the character of Shaggy on Scooby-Doo.
The ProtestIn the weeks leading up to Tuesday's protest, Kerri says, she contacted adult protective services who attempted to pay Kasem a visit, but they did not enter the home for reasons that remain unclear. (A spokesman for the department said their investigations are confidential.) The family then asked police to conduct a welfare check, and officers told them that Kasem appeared to be fine. (LAPD didn't immediately comment regarding the visit.) However, the family still hasn't been able to see their father.
"It's his isolation that we're most concerned about," says Kerri. "That's why we had to resort to the public protest, to send a message that we want to see our dad and aren't giving up. This has nothing to do with money or inheritance, because we're all self-sufficient. We're not in his will and we're completely fine with that."
Kerri says the family's next step is to take matters to court. "All we want is to see our dad," she says. "It's as simple as that."
PEOPLE reporter Ken Lee (below) talks about the unusual scene outside Casey Kasem's house