Here are a couple of census records from www.familysearch.org
which may fit. The first is from the 1850 census for Avon, Rock County, Wisconsinhttps://familysearch.org/pal:/MM9.1.1/M4DL-GDV
The next is from the 1860 census from Springdale, Dane County, Wisconsin. I saw an online tree at Rootsweb world connect, which said all of Knut and Valina's children were born in Dane County. This is from the census at Heritage Quest.
Sivert Knudson, age 38, born Norway
Ingeborg Knudson, age 37 born Norway
Knudt Knudson, age 11, born Norway
There is also a Knudt Knudson, age 30, living next door, possibly a brother to Sivert?
Vortha Knudson, age 11, born Wisconsin, female
in the 1880 census, Knud Syverson is in Blue Mounds, Dane Wisconsin, and his Mother, Betsey Syverson is lving with him