There are a few relatives that I've had a hard time making progress on.
Andrew Frederickson and his daughter Ida J. Frederickson (Erickson married name) from Finland.
Ida married John A. Erickson and his mother is listed as Maria________UNK___ also from Finland.
I've tried using the Finnish database but I'm not having a ton of luck since there are a variety of possible names (ex Andrew could have been Anders, etc) I know that Frederickson was probably spelled Fredriksson and his father's name was probably Fredrik)
Also, on a different side - Wiik in Norway which became "Wick" in the USA:
I've also tried using the Norwegian databases to find a Johannes Wiik and his wife Bertha _________UNK_____ which come up on one census but I can't find any information about them as kids to take the family line back further.