Marius Borg Hoiby has no royal title or duties, but as the stepson of the heir to the throne, his arrest has cast a cloud over Norway’s popular royal family.

Police in Norway have arrested the 27-year-old son of Crown Princess Mette-Marit on suspicion of rape, saying the alleged victim was "unable to resist the act."

Marius Borg Hoiby, 27, is under arrest for suspicion of rape involving someone who was unconscious and otherwise incapable of resisting the act, Norway Police announced on Tuesday.