Roadblock in Eidsvold family history

My great-grandfather was Andreas Andersen b. 7 Oct 1835(on death certificate) (may vary) in Eidsvold, Norway. 1865 census 6062 23 living on Vestengen Krogen 1. He came to America leaving Oslo 9 June 1871 on the Hero (don't know the transatlantic vessel). His wife and family left on 11 Oct 1872 on S/S Oder (am not able to find passenger record). They settled in Jackson County, Wisconsin and he took the surname Berger because he had worked at the Berger Glass factory in Eidsvold. He had a half-brother named Anton Anderson b. around 1860 and half- sister named Maren Andersdatter b. 19 Feb 1857. I have pictures of them. Both were born in Norway and I think in Eidsvold, but I find no record of them in census, confirmation or emigration records. They both came to America. Maren settled in La Crosse County, Wisconsin and Anton maybe in Jackson County. It may be that the half-siblings come from either mother or father of Andreas. Any suggestions will be most appreciated. Thank you. Mary