Just days prior, newly released US documents revealed Høiby's mother, Crown Princess Mette-Marit, maintained extensive contact with convicted sex offender Jeffrey Epstein between 2011 and 2014.
Police in Oslo detained the stepson of Norway's crown prince on Sunday, accusing him of assaulting a woman, threatening her with a knife and breaching a restraining order just two days before he faces trial on multiple rape charges.
Marius Borg Høiby, 29, will appear in Oslo district court on Tuesday charged with 38 offences including four alleged rapes and attacks on former partners. Prosecutors are seeking to hold him in custody for four weeks, citing concerns he may reoffend.
"Oslo Police District can confirm that Marius Borg Høiby was arrested by police on Sunday evening," authorities said in a statement Monday.
Just days prior, newly released US documents revealed Høiby's mother, Crown Princess Mette-Marit, maintained extensive contact with convicted sex offender Jeffrey Epstein between 2011 and 2014.
Her name appears at least 1,000 times in the documents released by the US Department of Justice on Friday, according to Norwegian media.
Mette-Marit apologised on Saturday, calling her contact with Epstein "simply embarrassing" and saying she showed "poor judgment". The palace confirmed she stayed at Epstein's Palm Beach residence for four days in 2013 and met him on several occasions, although she never visited his private island.
Mette-Marit married Crown Prince Haakon in 2001, bringing her son from a previous relationship into the Norwegian royal family. The crown prince is heir to the throne.
The defendant has acknowledged some lesser charges but contests the most serious allegations.
Multiple former girlfriends have joined the case as plaintiffs. A court order prohibits him from contacting them.
If found guilty, Høiby could receive a maximum sentence of 16 years. The proceedings are scheduled to continue until mid-March and have generated significant public interest in Norway.