I have found Thor Syversen in the Norwegian sources through his wife Olava Olsdotter Hoaas, who is a distant relative of mine. They married i 1869 and settled in Fræna, a municipality on the coast of the county Møre og Romsdal, the municipality in which I now live. Here they had 3 children: Syver Olaus who died only 5 days old, Olaf and Thomas twins in 1871. Then the family moved first to Støren in Sør-Trøndelag (some 30 km south of the midnorse city Trondheim)where Thor Syversen was a railway worker. In Støren they had the son Simon Johannes in 1873, and then they moved further inland, to Aalen (along the railway from Trondheim via Røros to Hamar and Oslo. Here they got the son Ole Mathias in 1875. That is what I know about the family now. But I know Olava Olsdotter Hoaas her ancestors back to 1600, Thor Syversen came from Heidal in Vaagaa parish in Oppland county (middle south Norway, up to the mountain heart of southern Norway, Jotunheimen). It is possible he came to Fræna together with relatives, for the farm he first lived at, Slutaas, is a part of Aas farm, where also people from Heidal settled (A descendant of these people has been a colleage of mine).So I will look into that.
Magnar Husby (Husby family tree at ancestry.com)