The millionaire co-founder of MoneySupermarket.com who discovered the three boys he raised were not his own has offered a £5,000 reward to find their real father's identity and will drop hints in an upcoming book, it was revealed today.

Richard Mason, 55 – who was told by doctors that he was infertile in 2016 – believes the children were the product of his ex-wife Kate's affair and admitted he considered suicide in the aftermath.

He only made the shocking discovery when he was diagnosed with cystic fibrosis and told the genetic condition meant he could not have children because most men with it don't have a sperm canal.

The millionaire MoneySupermarket.com co-founder shot back: 'You must have got the diagnosis wrong because I've got three sons.'

After initial denials, his now ex-wife Kate admitted an on-off affair with a colleague during their 20-year marriage, but refused to name him and said they always used contraception.

The co-founder of price comparison site had been a doting father to the boys and said yesterday the shock of discovering the truth left him contemplating suicide and is now planning to write a book about his experience.

The eldest is 23 and a budding businessman, while the 19-year-old twins are at university.

Richard Mason, pictured with ex-wife Kate and sons in 2014, has offered £5,000 for information to help find the biological father of the three boys he raised as his own

The businessman said when he found out that he couldn't be the boys' (pictured as children) father his first thought was 'S***, my life is ruined'

'I still regard them as my boys even though I'm not their biological father, and I miss them so much,' he added.

What is cystic fibrosis-related diabetes? Cystic fibrosis is an incurable genetic disease that affects around 70,000 people worldwide. A defective gene causes a build-up of mucus in the airwaves, making it increasingly difficult to breathe over time. Mucus also blocks the natural release of digestive enzymes, meaning the body does not break down food as it should. While healthy people cough naturally, that does not happen for people with CF. Eventually, lung function depletes to the point that sufferers will need a double lung transplant to survive. Thousands of sufferers will go on to develop diabetes, as the build-up of mucus can prevent the pancreas from working properly. Cystic fibrosis-related diabetes is most often treated with insulin, a hormone that helps control blood sugar levels. Most men with CF are infertile because of a blockage or absence of the sperm canal. Advertisement

Two of the three boys refuse to speak to him but one recently texted him to say: 'Dad, as I explained from the beginning you would never not be dad to me regardless of all this.

#Of course I'll stay in touch, that will never change… I'm always here for you too and you will always be Dad. Love you x.'

Describing the turmoil in his life Mr Mason said yesterday: ‘You don’t know what’s real and what isn’t – it’s as if I’m living in The Matrix.

'Someone says to you, “All that you know and everything you thought to be solid and true is not real, and never did exist. You are not a father, you are not able to have kids, your name will not continue.”

‘I still see what the boys are doing on Facebook and it’s heart-wrenching because we saw the graduation of the eldest on there, but I wasn’t invited.

‘I walk past a toy store and it reminds you of buying Christmas presents for them and other family occasions.

‘And when friends post things on Facebook about their own families like their first grandchild or saying they’re proud of their boy for something, I just think, “My God, that’s all been taken away from me.” ’

Mr Mason, now remarried, said his ex-wife ‘tricked’ him into believing the boys were his, when at the very least there must have been some doubt in her mind – not least because she only became pregnant seven years into their marriage.

‘After the divorce, she constantly hounded me for more maintenance even though I always complied with the Child Support Agency demands,’ he said.

‘Meanwhile, the biological father has never paid a penny as far as I know.’

Mr Mason is offering £5,000 for information to help him identify the real father, who is not thought to have contributed financially to their upbringing.

Despite Kate's insistence on giving all three boys Jewish middle names – even though neither of them followed the faith – and refusal to have them christened, he had no idea he was living a lie.

It was only in 2016, almost ten years after they split up, that doctors told him he had cystic fibrosis.

At the time he and second wife Emma were trying for a baby, but the doctor warned him the genetic condition meant he was infertile. Mr Mason recalls saying: 'You must have got the diagnosis wrong because I've got three sons.'

But the consultant told Mr Mason that the only father with cystic fibrosis he had ever known later discovered he had been duped by his cheating partner.

After he quizzed Kate, she sent him a message insisting: 'Of course the boys are yours, no matter what the science might suggest.'

Shortly after, according to the Mail on Sunday, she admitted to an affair with a work colleague at Barclays in the 1990s but insisted she had genuinely believed her husband was the boys' father.

Mr Mason, pictured with wife Emma, said: 'I still regard them as my boys even though I'm not their biological father, and I miss them so much'

Mr Mason launched a paternity fraud claim and demanded she pay back some of the £4million divorce settlement which funded their private education, as well as her new life in a seven-bedroom home.

Now, in what is thought to be the first case of its kind, 54-year-old Kate has agreed to repay him £250,000 in an out-of-court settlement. However, the bitter dispute has almost destroyed his relationship with the boys.

The eldest vowed never to speak to him again if he took legal action against his mother, who has a new partner, while only one of the twins replies to his messages.

Mr Mason is struggling to come to terms with being childless, while Emma is unable to conceive following a battle with cancer.

Yesterday at his £650,000 detached home in Rhos-on-Sea, near Llandudno, he told of his anguish. 'Imagine being told you are going to die and your three sons are not your own – my life fell apart,' he said. 'But what stopped me was the love I feel for Emma. She is my soulmate, and has got me through all this trauma.'

A man who answered the intercom at the former Mrs Mason's £1million home near Uttoxeter, Staffordshire, yesterday said she was on holiday, while her sons did not respond to messages.