Johannes is born 31 JUL 1837 in Lærdal, Sogn og Fjordane, Norway. The familytree that I've linked to in Anna Anderson's topic, list Johannes as emigrated from Drammen, Norway in 1865.
Did you check in the Lærdal parish records for that marriage?
There were men in that area named Sven or Svend and I see no reason that they couldn't have daughters who were marriagable.
When you are given information that you find doubtful -- check the primary sources! It isn't unusual to find work not well done that needs much research to make right.
You've learned how to do this -- apply what you've learned.
10-4 Hopkins. I will check, also, Thanks for that link on the church record information. I added it to my favorites as I still go back to that page to check stuff. Thanks again.