He may have been just 16, but the steely gaze with an underlying hint of menace is unmistakeable. It is a look that would become Kevin Spacey's trademark and which would help him earn two Oscars, an honorary knighthood from the Queen – and a £60 million fortune.

Scrawled on the photograph, in fading ink, is a cheery message to his older brother Randy: 'I will invite you to the Academy Awards when I go!'

If the inscription seems optimistic and a touch naive, it was, says Randy, written against a background of dark family secrets and lies – a 'world of deviancy and betrayals' that Spacey's brother claims gives a chilling insight into the American Beauty star's spectacular fall from grace last week amid claims he sexually molested men throughout his career, including a 14-year-old boy.

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Randy Fowler, Kevin Spacey's older brother, said this picture - sent to him by the actor with a caption vowing to take him to the Oscars should he ever be invited - marks 'the moment my brother turned into this creature whose life was a lie'

Randy recalled suffering sexual abuse at the hands of his Nazi-sympathiser father Thomas (pictured left with wife Kathleen and Kevin) and said his brother used fame and fortune as a way to hide from his past

'This picture is the moment my brother turned into this creature called Kevin Spacey, says Randy, 61. 'And that creature turned into a monster whose whole life was a lie.'

Today Spacey's reputation lies in tatters. He has announced he will seek psychological help to tackle his demons, but his career is effectively finished.

His award-winning Netflix series House Of Cards has been abruptly terminated amid reports that eight members of the show's crew have accused him of sexual misconduct.

And the man who single-handedly saved London's Old Vic theatre during his 11 years as the famous playhouse's artistic director has been dumped by his agent.

Today, in an extraordinary interview, Spacey's brother sheds new light on this astonishing fall from grace, and what he calls the 'demons' driving the tarnished star.

He tells how they were brought up in a monstrous 'house of horrors' where the children were systematically beaten, starved and abused by their neo-Nazi father. And he says his millionaire brother effectively 'abandoned' his family because he wanted to distance himself from the demons of their shared past.

Randy says Spacey's decision to mask his true self has left the actor 'a time bomb', adding: 'He sold out to fame and fortune, but the truth was always going to catch up with him.

'This is just the tip of the iceberg. He has used his fame, power and money to prey on those more vulnerable than him. This behaviour has been going on for decades.'

At 58, Kevin Spacey is an instantly recognisable Hollywood star. His brother, meanwhile, cuts an eccentric and slightly sad figure, as he sits in a toy-filled room in his modest home in a working class suburb of Boise, Idaho, a city in the American West famed for its production of potatoes.

Randy is something of a local celebrity thanks to his job as a Rod Stewart lookalike limo driver. For our interview he wears an extraordinary canary yellow suit, his hair is gelled, he has rings on every finger.

He explains the toy-filled room, saying: 'As kids we never had toys. This room makes up for the childhood we never had.'

He admits there have been times when he has resented his brother's fame and success but, as he talks, the story that emerges is compelling – and utterly believable.

Randy (pictured right with his brother in adolescence) said that he has learned to come to terms with his demons in a way that Kevin never did

Randy currently works as a Rod Stewart impersonator and drives limousines

'Yes, Kevin has been more successful than me financially and professionally, but I've learned to cope with my demons and I don't think he ever came to grips with his,' Randy says sadly.

Kevin, born Kevin Spacey Fowler, was the youngest of three children.

The boys' elder sister Julie, now 66, fled home at 18 and married a Scottish former football player, Ian Keir.

Their father, Geoff Fowler, was a writer for technical magazines but was frequently out of work, moving the family ten times before Kevin was 14.

The family moved to Los Angeles when Spacey, who was born in South Orange, New Jersey, was a toddler.

In one of Spacey's many interviews, he refers to his childhood, saying: 'When some people think of home they think of a place where they grew up and had all their Christmas dinners and family gatherings. I don't have that.'

Randy says Kevin's careful description of his past was a calculated 'reinvention' to mask the horror of their childhood.

'Our father was a Neo-Nazi who had a photograph of Adolf Hitler on the mantelpiece. He had swastika armbands, the lot. At one point he even grew a Hitler moustache.

'He was a violent and abusive man who would whip us with a riding crop if we were out of line. We lived in a house of horrors.'

The abuse turned to terror when Randy was 14. 'That's when Dad raped me for the first time. He pushed my face down into the pillow. I was screaming.

'I heard Mum at the door and I begged for help but she walked away. I have never felt so alone.'

Spacey's career is effectively over after being accused of a string of sexual abuse spanning decades and two countries

Randy declines to comment on whether his siblings were abused, saying simply: 'That is for them to discuss if they want to. But when I saw Kevin had been accused of molesting a boy of 14, the same age I was when Dad molested me, a chill ran down my spine.'

Theirs was, he says, a cold, unemotional, Victorian household.

'Feelings were never discussed. Our father, who we nicknamed The Creature, would rant about Nazi stuff for hours. There were times we didn't have enough food on the table and went hungry.

'He took us on holiday to a nudist colony. What sort of father takes his kids to a nudist colony?

'In his office, Dad had books of child pornography.

'Kevin was a shy, quiet child, a mummy's boy. He was sweet but didn't stand out from the crowd. We built forts, rode bikes, escaped outside as much as we could.'

He proudly shows off pictures of his brother, including an early promotional shot of him in fencing gear (taken in April 1976 three months shy of Kevin's 17th birthday) for his burgeoning acting career.

'I took that picture and that's when Kevin's name changed. He was always Kevin Fowler but that day I said to him, 'That's not a proper actor's name.'

'His middle name is Spacey which I said sounded more like a movie star. From that day on he was Kevin Spacey.

'He was a natural on stage. He loved the attention. He loved playing at being someone else.

'Once he started acting he realised the power he had, it transformed him. He created the character of Kevin Spacey but it masked a monster.'

Spacey thrived on complex, sinister yet utterly mesmerising characters such as politician Francis Underwood in House Of Cards and crime boss Keyser Soze in The Usual Suspects.

'Fans love the sinister characters he plays, but what they don't realise is he's not acting, that's really him. When he changed his name his life started to become a lie.

'He became a ticking time bomb. He hid behind a mask of fame. The richer and more famous he got the more he lived a lie. The world fell under his spell but I've long suspected there is a dark side to him.

'He has reinvented himself constantly and I believe it was to forget the horrors of our childhood.'

Randy, who has been married and divorced three times and now lives with Trish, his companion of 23 years, was never in doubt about his brother's sexuality.

Gay rumours have dogged Spacey for years, but it was only last week, after Star Trek actor Anthony Rapp claimed Spacey sexually abused him when he was 14, that Spacey officially came out as homosexual and said that he couldn't recall the encounter but apologised for 'what would have been inappropriate drunken behaviour'.

Spacey's mother Kathleen pictured with her husband, who took to wearing traditional highland dress after their daughter married a Scotsman

Randy says: 'Kevin never had a girlfriend. Of course I knew he was gay, we all did. I never saw him with any girls.

'The only people he loved as a kid were male stars like Frank Sinatra and Christopher Walken.'

When their mother Kathleen won nearly $2million on the lottery in 1985 she willingly invested it in Kevin's career.

Her generosity was repaid when Kevin set his mother up in a luxurious home in the upmarket Pacific Palisades area of LA.

Randy says: 'He paid for everything, he took her to the Oscars, he treated her like a queen. Her home was a shrine to Kevin Spacey, I was shocked because I couldn't see a single picture of me.'

The brothers have met only five times in nearly three decades, one of them when their father died in 1992. 'We never fell out, but the bigger Kevin got, the more distance he put between us,' Randy says.

'Year after year he would ignore me, and the older Kevin got the more cruel he seemed to become.'

In 1989 the pair visited their parents, then living in Seattle, and shared a marijuana joint. 'I asked Kevin if he was gay and he said, "I'm not heterosexual, homosexual or bisexual, just sexual." '

As Spacey's career took off, in New York as an acclaimed Broadway actor and then Hollywood where he transformed into a bona fide movie star, he started to push Randy out of his life.

'I felt hurt. What sort of person abandons family?

'I think he did it because I reminded him of Kevin Fowler and where he came from.

'I used to watch everything he starred in but it's been years since I could stomach seeing him in anything.'

When their mother was taken ill with a brain tumour in 2002, Randy says Kevin 'acted like a hotshot' at her hospital bedside.

'He was arrogant. I was horrified at how rude he'd become and told him so. He plays arrogant, twisted people and some of that rubbed off on to the person he became.'

The last time Randy saw his brother was in 2003, after their mother died. 'Kevin organised the funeral and all his work friends came, which I thought was weird.'

Randy says his brother's carefully crafted facade began to crumble in 2004 when he was allegedly 'mugged' in a park in Lambeth, South London, at 4am.

Spacey later dropped charges against the man amid rumours it was an attempted sexual liaison gone wrong.

Randy says: 'That's when the wheels of his fake life started to come off. I thought then it was only a matter of time before the world would know the real Kevin Spacey.'

Last week several former actors and employees of The Old Vic accused the actor of inappropriate sexual behaviour and Scotland Yard is investigating.

Randy says: 'What saddens me is he used his fame and power to take advantage of people. That's wrong. Our childhood scarred us all and left me so terrified that my father's evil personality could be passed on that I chose to never have children. Now it seems my father's twisted genes may have been passed on.

'Our father was a monster and Kevin turned into a monster.'

Randy, who has written an autobiography, A Moment In Time: Living In The Shadows, tried to contact his brother last week through the actor's manager but has heard nothing.

Randy says: 'I know Kevin Fowler, I don't know the person he became but I will always love him. I hope he gets the help he needs.'

Additional reporting: Sharon Churcher and Peter Sheridan