'I am known for being Mamma's son': The mystery surrounding Marius Borg Høiby's biological father

"I am known for being Mamma's son. Nothing else."

Those were the words spoken by Marius Borg Høiby on the second day of his trial for rape and assault, which began in Oslo this week.

He is the son of Norway's Crown Princess Mette-Marit, born before she married the country's future king in 2001.

But little is known about his biological father who has been noticeably absent during the criminal trial, which is expected to last seven weeks.

The case has captivated Norway and drawn interest from around the world, while threatening to permanently damage the royal family's reputation.

Høiby has denied four allegations of rape as well as other serious charges against him. If convicted, the 29-year-old faces 10 years in prison.

Høiby is not a member of Norway's Royal House or a public figure, but grew up as part of the royal family, attending many events with the King and Queen and the Crown Prince couple over the years.

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He stepped back from public life in 2017.

Høiby was four when his mother became Crown Princess of Norway and after the wedding, his new stepfather Crown Prince Haakon held him in his arms during an appearance on the royal palace balcony.

Høiby was nicknamed by the press as 'Little Marius' and was pageboy at the wedding.

Crown Prince Haakon, 52, has always been close with his stepson and last week, days before the trial began, he affirmed his support for Høiby and the alleged victims.

"Marius Borg Høiby is not part of the Royal House, and in that sense he is free," Crown Prince Haakon said.

"He is an important part of our family. He is a citizen of Norway, and through that he has the same responsibilities as everyone else, but also the same rights."

The King and Queen and Crown Prince have carried on with their official duties and the Royal House said no-one from the royal family would attend the trial.

Crown Princess Mette-Marit's planned private trip had now been postponed "until further notice", the Royal House said. She was due to be away from Oslo during the trial but on Saturday, the Crown Princess issued an apology after being named in the newly-released Epstein files.

"I deeply regret this, and it is a responsibility I must bear," the Crown Princess said.

"I showed poor judgement and regret having had any contact with Epstein at all. It is simply embarrassing."

Høiby's biological father has chosen to avoid the very public trial, too.

Morten Borg has largely remained out of the spotlight over the years. Recently, he was approached by Swedish journalist Niklas Svensson in connection with the documentary The Truth About Bonus Prince Marius Borg Høiby.

Borg was asked whether he would attend his son's trial.

"I understand what you want, but I have nothing to say," Borg said, according to a translation.

Borg was briefly mentioned by Crown Princess Mette-Marit in the NRK documentary, The Year with the Royal Family – a program that is made each year and covers the monarchy's work.

In the documentary, which saw a crew from Norway's national broadcaster travel to Australia to film a segment on Princess Ingrid Alexandra's move to Sydney, Mette-Marit spoke about Høiby's father.

She said Borg was still involved when it came to getting the necessary and professional help for their son.

Days after Høiby's initial arrest in August, 2024, he issued a statement admitting to experiencing "challenges" over the years.

"I have several mental disorders which mean that throughout my upbringing and adult life, I have had, and still have, challenges," Høiby said.

Høiby's alleged "challenges" are well-documented in Norwegian media.

"There are reports – or rumours – about Høiby and his life," royal correspondent at Norway's national broadcaster NRK, Kristi Marie Skrede, told nine.com.au.

"Høiby has said publicly that he had mental issues growing up and that he for some years now has struggled with alcohol and drugs."

Borg – an entrepreneur and prominent figure on the Oslo party scene – and Mette-Marit had a brief relationship in the mid-1990s.

He had previously been jailed for drug offences. Some reports suggest Borg was in prison when his son was born.

Mette-Marit later met Crown Prince Haakon in 1999 through mutual friends.

In the 15-month lead up to the royal wedding, much was made about Mette-Marit's past and the fact she had a young son.

Days before the wedding, Mette-Marit Tjessem Høiby – as she was then known – apologised for her rebellious days.

"My youth rebellion was much stronger than many others," Mette-Marit said in a press conference.

"That resulted in me living quite a wild life. We overstepped the limits.

"It was a costly experience for me, that I took a long time to get over."

"I would like to take this opportunity to say that I condemn drugs," she said, before adding: "I cannot make these choices again, even though I would wish I could".

Høiby's teenage years, and his 20s, were littered with similar experiences.

In addressing the court on the second day of his trial, Høiby told the judges: "Few can relate to the life I have led. A lot of parties, alcohol, some drugs."

He also described being followed by the press since he was three-years-old.

In The Year with the Royal Family Crown Princess Mette-Marit said she had been particularly upset by some suggestions she and the Crown Prince failed in their responsibilities to Høiby.

"What perhaps makes me most upset is being criticised for how we have handled this as parents," she said.

"That we haven't taken it seriously. I find that difficult."

Mette-Marit added: "All parents – perhaps especially parents who have been in the situation we have been in – can probably relate to the fact that there is an incredible amount of self-blame involved."

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