Frail boxing legend MUHAMMAD ALI is at the center of a vicious family feud, The National ENQUIRER has learned exclusively.

The famed athlete’s only natural son claims Ali’s wife of 27 years, Lonnie, is blocking his nine children from seeing their Parkinson’s-stricken father.

Muhammad Ali Jr. believes that he and his siblings – not Lonnie – should oversee their father’s care, and they may go to court to fight for visitation rights, as well as conservatorship of their ailing dad.

“I can only speak for myself, but we don’t get to see my father as much as we’d like to. We’re considering taking legal action,” the 42-year-old Ali Jr. told The ENQUIRER in an exclusive interview.

His comments echo claims made by Ali’s heartbroken brother Rahman, who told The ENQUIRER that Lonnie – whom he once called “evil” – was draining Ali’s $50 million fortune and keeping him “a prisoner in his own home.”

Ali Jr. added: “It’s not that Lonnie is all about caring about my father – it’s all about what she can get. We would prefer to see his care in control of the family.

“We want to get power of attorney over my father. We love him, and we can take care of him as he should be cared for.”

According to Ali Jr., he and his eight siblings – seven sisters and one adopted brother – want to take legal action when “the time is right.” But insiders say any such legal action is sure to face “fierce resistance” from Lonnie – who is Ali’s fourth wife and has looked after him ever since he was diagnosed with Parkinson’s disease in 1984.

While there are conflicting versions of the true status of Ali’s health, one of his personal physicians, Dr. Abraham Lieberman, told The ENQUIRER: “I see Muhammad every couple of weeks, and some days are better than others.

“That’s how this disease can manifest. When he’s rested, he appears much better and improved. He tries to stay as active and involved as possible.”

“He’s always excited to meet people and attend fund-raising benefits.”But Dr. Lieberman, a co-founder of The Muhammad Ali Parkinson Center, pointed out: “Unfortunately, there are no new drugs available to treat this progressive disease.”

“The Greatest” is expected to appear Sept. 27 at the 2014 Muhammad Ali Humanitarian Awards ceremony and related events, including a “Today” show appearance, in Louisville, Ky.The former heavyweight champ is the subject of a new documentary, “I Am Ali.” Set for release Oct. 10, it goes behind the scenes of his brave battle with Parkinson’s.

Despite Lonnie’s interference, Ali Jr. said he spoke to his father this past Father’s Day after posting a plea on Facebook.

“It was a short conversation,” Ali Jr. told The ENQUIRER. “I guess he was doing okay, but it’s hard to tell unless you see him.”

In response, a statement from the champ’s family to The ENQUIRER said: “The allegations made by Muhammad Ali Jr. concerning Lonnie Ali are completely false. Muhammad’s children have always visited their father as their and his schedule allow … the Ali Family feel that Muhammad Jr. is being manipulated to make false claims to the media, possibly for monetary gain.”