Foss in Livingston Montana

Three siblings called Simonsen left Norway for US about 1920: I am searching children and children's children to Chris Foss (Kristen Fossaas Simonsen) 1890-1978 and Dagny Foss 1894?-1987. They were both born in Vestfold, Norway. (Chris also had a brother and sister that emigrated to Livingston - and I am getting back to them later. He was a brother of my mother's mother.)