Norwegian Names is one of the reasons I don't use FTM for most of my genealogy, It is not good at all with non-western naming convensions. It does not understand "no surname", or multiple surnames, or clan names.
1) Norwegians born and living in rural Norway before 1924 did not have real surnames.
2) Many indviduals in Norway appear to change names as they move around. This of course is not true but to western eyes and logic they are.
3) Individuals in the same house and generation could have different surnames in 1924. i.e. Two brothers could have different surnames
4) Individuals with true surnames have spelling differences.
5) If you can go back far enough people appear to have a "clan" name, just like they do in Ireland and Scottland.
5) People had "patronymic names", "geonymic names" sometimes they became surnames sometime they did not.
6) Some modern Norwegians are using a combination of inherited paternal names for their children. Much in the fasion that South American, Spanish and Portugues names are.
If you don't understand this, that's OK I've been doing Norwegian Genealogy for 20 years and most people I talk to have trouble.