Ylvisbrother are from Bergen and I think this was from Oslo. Their dialect are quite different from Oslo and eastern norewegian dialect which I think a lot of foreigners think is true norwegian. But true norwegian are all de other over 1200-1300 dialects from rural Norway.
They are all from Bergen or well Ylvis are from Sogn but grew up in Bergen, except the early years in africa. And this is from Oslo, if it was in Bergen I would say it was more likely. But sure it’s easy to find connections here in Norway.