A waif-like 25-year-old is not only determined to marry CHARLES MANSON – she also wants to have the madman’s baby!

A source says that’s the shocking secret behind the evil 79-year-old’s stunning revelation that he plans to wed the groupie that he’s nicknamed Star.

The notorious murderer
 boasted about their bizarre relationship in a recent interview, and now The ENQUIRER can reveal intimate details of the couple’s sick, twisted life and their plans for a future together.

“Star is ‘madly’ in love with Char- lie, to use the word loosely – and she’d like nothing better than to have his baby,” said a close source.

Manson is serving a life sentence at California’s Corcoran State Prison for his role in the brutal 1969 murders of movie director Roman Polanski’s actress wife Sharon Tate and Los Angeles residents Rosemary and Leno LaBianca – and Star visits him regularly there.

While prison regulations would allow the couple to marry, conjugal visits for inmates serving a life sentence are forbidden. But Manson could conceivably sidestep that rule, said the source.

“Anything is possible, the source pointed out. “Manson could attempt to have a sample of his sperm smuggled out of the prison so Star could impregnate herself – or even persuade guards to look the other way while they have a quickie.”

The “Helter Skelter” fiend boasted in “Rolling Stone” magazine that he spends up to 10 hours every weekend with Star in the prison’s visiting area.

Star bears an eerie resemblance to Manson disciple Susan Atkins, whom he called “Sexy Sadie” after The Beatles song.

Atkins was sent to prison for life for the brutal Tate-LaBianca killings and died behind bars in 2009.

But in the interview, Star insisted
 that she doesn’t want 
to be compared to At
kins, who gutted the 
8 1/2-months-pregnant actress while Tate begged for her life.

Referring to Atkins, Star snapped: “That b**** was f ****** crazy… She didn’t know what she was doing.”

Star says she was raised by strict Baptist parents near St. Louis, Mo. When she refused to attend church and began taking drugs, they locked her in her bedroom.

She’d never heard of Manson but became enthralled with the wild-eyed cult leader after reading that he believes “Air is God, because without air, we do not exist.”

She began writing to him, and when she was 19, she used $2,000 in savings to move near Corcoran so she could be close to her idol.

The unlikely pair began a relationship, and in a series of photos posted on Manson’s website, Star cuddles with the depraved killer.

Other shots show her with a shaved head and the same “X” carved into her forehead that other brainwashed members of the Manson “family” copied during the trial.

She lives in a cramped apartment near the prison, and when she’s not with Manson, she spends her time online, devoting herself to re- habilitating his image and ordering goodies for his quarterly-allowed gift box.

In the interview, Star defended their odd courtship, saying: “Yeah, well, people can think I’m crazy, but they don’t know. This is what’s right for me. This is what I was born for.”

She adds: “I’ll tell you straight up, Charlie and I are going to get married. When that will be, we don’t know. But I take it very seriously. Charlie is my husband.”

But an expert who has not met Star says her fascination with Manson is a classic case of rebellion.

“Star’s seeming infatuation with this mass murderer, while obviously highly unusual, appears to be a classic case of a young woman wanting to rebel against her strict family upbringing,” Dr. Robi Ludwig, a psychother- apist and host of the TLC program, “One Week to Save Your Marriage,” told The ENQUIRER.

Ludwig has not treated Star.

“She may also enjoy the reflected attention she gets from being part of this infamous and notorious criminal’s life.”
Manson, who was denied parole for the 12th time in 2012, has two ex-wives and at least three children.

In prison, he’s befriended fellow inmate Phillip Garrido, the creep who kidnapped Jaycee Dugard when she was 11 and raped her repeatedly while keeping her prisoner for 18 years.

Looking ahead, Star says if Manson is released, they’ll move in with her family.
“My parents like Charlie,” she noted in the interview.

“They said, ‘If Charlie gets out, you guys can come stay here.’ ”
But Dr. Ludwig warns that living with a man old enough to be her grandfather wouldn’t be easy.

“As long as he’s in prison, she can keep him at arm’s length,” Dr. Ludwig said. “But if they lived together as man and wife, being with him could lose a lot of its luster.”