Man learns father is Charles Manson

A US man has revealed his anguish over learning that his father is serial killer Charles Manson.

Matthew Roberts was given up by his biological mother soon after his birth in 1968 and lived happily for decades before learning the truth about his origins.

"It's like finding out that Adolf Hitler is your father," he was quoted by The Sun as saying. "I'm a peaceful person trapped in the face of a monster."

Roberts became obsessed with discovering his true identity after one of his sisters told him he was adopted.

He contacted his biological mother Terry through a social services agency and soon learned his real given names — Lawrence Alexander — but she refused to reveal his surname or the identity of his father.

But after a series of pleading letters, Terry admitted the truth: she had run away to a hippie commune after being seduced by Manson, despite warnings from her father that he was a "white-trash biker bandit".

They ended up in San Francisco, where Terry claims she was raped and impregnated by Manson during a drug-fuelled orgy before she returned to her family home.

Allegations that Roberts is Manson's son are supported by their strong resemblance — they share the same eyes, nose, mouth and large forehead while Roberts has unwittingly followed his father's path into music and poetry.

The pacifist vegetarian is also concerned that he has inherited his father's schizophrenia and tendency for violence, even though he is adamantly against such activity.

"I'm not nuts but I've got a little bit of it — it's scary and upsetting," he told The Sun.

"If I get worked up, my eyes get really big and that's really freaked out some people before."

Roberts has also struggled with his decision to make contact with Manson.

The homicidal cult leader has sent 10 notes and postcards to his biological son since contact was first made seven years ago — all of them signed with the Nazi swastika.

"At first I was stunned and depressed … I wasn't able to speak for a day, I remember not being able to eat," he said.

In the letters, Manson recalls meeting Terry and hints that he is Roberts's biological father.

But despite the relationship, Roberts has not yet been able to bring himself to speak to Manson over the phone even though he admits to feeling "some kind of emotional affection".

"That's the hardest thing of all — feeling love for a monster who raped my mother," he says.

"I don't want to love him but I don't want to hate him either."