Looking for Torbjorn Tarkjelson Tveit and family

I am stumped. I have been searching for Torbjorn Tarkjelson Tveit b-1859, Bygland, Aust-Agder, Norway - his wife Torbjorg Tellefsdatter Kvinen b- June 6, 1854 Kviplassen, Bygland, Aust-Agder, Norway and their children Eivind Torbjornson Tveit bor Feb 12, 1882 in Bygland, Norway and Torbjorg had a daughter Torbjorg Knutsdatter Hegland bor Sept 18, 1876 in Bygland, Norway. Torbjorn, Torbjorg and son Eivind came to America in 1882. Torbjorg's daughter Torbjorg came in 1900. I think they all died here but I have done many searches and cannot find them anywhere. Are there other ways that I can look for them? Any help would be appreciated. It is like they all disappeared when they got to America.