Looking for Rosenbergs in Norway

My great-grandfather Carl Edwin Rosenberg (or sometimes spelled Karl Edvin Rosenberg) had 2 sisters - Anna, 1879 and Marie, 1885 - Rosenberg. Their father, Eilert Rosenberg, was a sailor, born 1842. I am looking for anyone related. My great grandfather was born 1883 in Frederikshald. In the 1900 census he is listed as "adopted or raised by foreigners" but church records revealed his parents named. His mother's name was Bernhardine Konstanse Rosenberg, 1857. At one time the family lived at Festningsgata 14. After Bernhardine's name it says: 1857 K Lysekihl Sv. I learned this through typing Eilert Rosenberg's name in a search engine (Google) and came up with a history link mentioning the 1885 census listing. A picture of the home also appears. I have information in Eilert's mother also. Her name is Caren Anna Johnsdtr. Rosenberg and is listed in the 1865 census as having lived at Saugoen in Idd. Eilert had 3 siblings - Johan Peter (Berg) and Laurits (Idd) and Inger Marie (Idd). Another search back to 1801 found one other Rosenberg: Helje Rosenberg - a Captain in an unamed branch of service. I don't know if he is related or not. Can anyone suggest help in finding relatives? If these names sound familiar to you I would appreciate your contacting me. I would also like to track the origin of the Rosenberg name. Thank you. Kathy