Nels Severtson

I am researching our family tree and am at a standstill. Our ggrandfather, NELS SEVERTSON,(also written on some documents as NILS SEVERTSON) immigrated to the United States in 1876. It states in his obituary in 1905 that he came from Thronjem's Stiff, Ytteroeen, Norway, and was born in 1845. We dont know who his family in Norway were and would like any information about the place he was born or his family. He married Mary Westman in Minnesota and they had four children Agnus, Jack, Henry and Mable. They were all born in Kanabec co. Minnesota. Nels and Mary are both buried at Brunswick Luthern Cemetery, in Brunswick township, Kanabec Co., Minnesota. Thanks in advance if you can help, Pamela Nels Severtson, 1845 Norway +Mary Westman 1879 Sweden = Mable Severtson 1903 Minnesota + Benjamin Heitmiller 1900 Minnesota =Phyllis Heitmiller Minnesota + John Trunk Minnesota = Steven Trunk 1957 Minnesota