Elfsater Family- Norway

Besides searching for Norwegian Howicks, I am also seeking info on Erik Elfsater born 1-5-1846 in Boverdal Norway. He died 6-22-1886 in WI. He was married to Eldri Ramstad and they had one surviving child, M. Lydia Elfsater Dahlen. I am looking to find out if Erik had any siblings and what his parents names might have been. Also, wondering when he came to the US. Any help would be greatly appreciated. Takk!