Tech billionaire Elon Musk's estranged father has had a baby with his own stepdaughter who is 42 years his junior, the Daily Mail reports.

The extraordinary revelation could provide the truth behind the bitter family feud that has engulfed one of the world's richest families.

Errol, 72, was branded ''evil'' and ''a terrible human being'' by the Tesla Motors chief, who said his father had done ''almost every evil thing you can possibly think of''.

Now MailOnline can reveal that South African businessman Errol has fathered a 10-month-old baby son by his stepdaughter Jana Bezuidenhout, 30, who was 4 when he married her mother.

Jana Bezuidenhout lived with Elon Musk as a youngster. Photo / Facebook
Jana Bezuidenhout lived with Elon Musk as a youngster. Photo / Facebook

In a sensational interview with MailOnline, Errol said he could 'barely remember Jana's mother Heide, despite the couple being married for 18 years and having two children together.

Elon, the 46-year-old SpaceX founder who has a £20 billion (NZ$39b) fortune, reportedly went ''berserk'' when he learned that his half-sister Jana, who lived with him as a youngster, was having his father's child.

Jana, a mother-of-two, declined to talk about the highly unusual family set-up when approached by MailOnline.

But a source close to the family confirmed Errol is the father of her baby boy Elliot Rush Musk.

They told MailOnline: ''Errol has known Jana all her life. It has split the family. Errol got married to her mother when Jana was 4 years old.''

Asked to confirm that Errol was the father of Jana's baby, the relative replied: ''That's correct.''

They said the birth had created a ''delicate situation'' within the family as Heide was trying her best to support her daughter while keeping the identity of her little grandson Elliot Rush's father a secret.

''There is not a lot of people who know this. We would actually like the facts to come out,'' they added.

Errol Musk, 72, was branded ''evil'' and ''a terrible human being'' by his son Elon. Photo / Getty
Errol Musk, 72, was branded ''evil'' and ''a terrible human being'' by his son Elon. Photo / Getty

Another relative told MailOnline: ''Errol got Jana pregnant. He is the father of her baby boy. But he was a father to her.

''The whole family was outraged when we found out. This is the reason why Elon is so angry with Errol. He is the only father she has ever known. And now he is the father of her child as well.''

For his part Errol, a successful consulting engineer, who lives in Langebaan, South Africa, revealed that a DNA confirmed he is the father of baby Elliot.

Though not discussing the family connection, he told the Mail on Sunday: ''I got my 30-year-old girlfriend Jana pregnant and we had a baby, who is now 10 months old.

''Of course I love him dearly, even though it wasn't planned. In my own cautious way I insisted on a DNA test to ensure he was mine.

''I told my daughter Ali about him because I thought she would be supportive and understanding. She said I was insane, mentally ill. She told the others and they went berserk. They think I'm getting senile and should go into an old age home, not have a life full of fun and a tiny baby.''

When the question was put to him Errol did not deny that his ''30-year-old girlfriend Jana'' is actually his step-daughter who he raised as his own child as a toddler, when challenged by MailOnline this week.

He replied: ''I have been single for 20 years. I have no step-daughters or step-sons. I have four ex-wives.''

Jana Bezuidenhout, 30, was 4 when Errol Musk married her mother. Photo / Facebook
Jana Bezuidenhout, 30, was 4 when Errol Musk married her mother. Photo / Facebook

Errol claimed he ''can hardly remember Heide'' and wouldn't recognise his second wife if he saw her in the street – even though his former wife lives in the close-knit community of South Africa's affluent western Cape.

He told MailOnline: ''Heide and I were married for a very short time.''

A craggily good-looking man with a 1000-watt smile and an easy humour, Errol still flies his own plane up the spectacular West Coast and has a fishing boat parked in the garage next to his silver Bentley Continental.

He refused to acknowledge that it was his relationship with his stepdaughter that had led to the rift with son Elon.

'I do not know what Elon's anger is caused by. It has been ongoing since we left the USA against his will in 2003,'' he said.

Heide, his second wife, was a widow with three young children when she met Errol.

Her first husband, Jock Bezuidenhout, died in a car crash and Errol helped raise her little ones Jock junior, Jana and Harry.

Errol already had three children of his own from his first marriage to high school sweetheart, the model and socialite Maye Haldeman – Elon, his brother Kimbal and sister Tosca.

He talks about spoiling his children and bringing them up in luxury. Musk senior was a millionaire before the age of 30.

''I drove them to school in a convertible Rolls-Royce Corniche, they had thoroughbred horses to ride and motorbikes at the age of 14. They were spoilt, I suppose. Maybe that's why Elon is acting like a spoilt child now,'' he says.

Elon has described this childhood as ''painful and isolated'', overshadowed by an absentee father who derided his eldest son's budding scientific brilliance.

Errol and Heide had two daughters called Alexandra ''Ali'' Musk and Asha ''Rose'' Musk.

Elon and Kimbal came to live with their father and Heide in their sprawling and well-equipped home in Pretoria, where the couple made no distinction between children and step-children.

Elon Musk told told American Rolling Stone magazine of his anger with his dad. Photo / File
Elon Musk told told American Rolling Stone magazine of his anger with his dad. Photo / File

Shortly before his 18th birthday Elon left South Africa to go to university in Canada, where his mother's family came from before moving to the US aged 24.

He encouraged his father to move to Malibu, California, and Errol, Heide, Jana and the rest of the children set up home there shortly after Elon made his multi-million-dollar fortune from the sale of PayPal in 2002.

Errol recalls feeling like a prisoner as he and Heidi plotted their escape, making secret appointments with the South African embassy to secure temporary passports before they fled back to South African in 2003 under a cloud.

Errol and Heide split up soon after and Jana and the other children were taken into the care of others.

Though naturally slim and blessed with piercing green eyes Jana has led a troubled life. She has battled drug addiction and was forced to bring up her first child, a little girl called Emily, on her own.

By contrast, Errol is described as a doting father to Jana's latest baby, supporting them financially and emotionally.

But despite his newfound love for his baby son, it has splintered one of the world's wealthiest families.

Elon, the space explorer who has started no fewer than four billion-dollar businesses told American Rolling Stone magazine of his anger.

''He was such a terrible human being, you have no idea,'' he told the interviewer with tears running down his face.

''My dad will have a carefully thought-out plan of evil. He will plan evil. Almost every crime you can possibly think of, he has done. Almost every evil thing you could possibly think of, he has done. It's so terrible, you can't believe it.''

The two men - whose egos clashed while Elon was growing up - have not spoken for 18 months.

''It is difficult to see how Elon will ever be able to forgive his father for what has happened. The family is split down the middle and we don't know how it will recover.''