Gunhilda Andrina Karlsdatter, Christiania Oslo No

I finally have a few more leads to go on for my Great Grandmother Gunhilda. She was born Nov. 27, 1869 in Christiania (Oslo) Norway to a Karl Larson and Marin Olava Jensdatter. Marin died due to complication from childbirth to Gunhilda and twin child. Gunhilda was sent to be raised by her Maternal grandparents; Gulbrand and anna Maria Jensen. Gunhilda took the last name of Jensen when she emigrated to the US in 1887. What I am looking for is information on her birth family. Other siblings to be exact. I know some where she has at least two brothers, I have been told their names were Gus and Alex. Those are the American versions I am sure. So possibly something like Gustav, Gustaf and Aleck, Axel? Not sure of all the name varations. So far I have not had any luck finding them in America but I know that they came here and lived and died here. Gus died in Florida and Alex possibly in Montana. I don't know by which last name they used I have been told both Calson, Carlsen, and Karlson, Karlsen!!! They could even possibly be half brothers? If anyone could find info on this family, I would love it! [:D]