I have found another Joseph & Rosalie Kapaun. The 1895 MN Terr. Census List Joseph age 45, in U.S. for 21 years, born in Austria. His wife is listed as surname Kapaun, given name Frodl, age 47?, born in Austria, in U.S. for 21 years. They have a daughter Christina, 24, born Austria; Son William, 17, born MN; and daughter Josephine, 15, born MN.
Passenger List for Josef Kapaun, Rosalie, and Christina from Bohemia(Michelsdorf/Lanskroun would be in Bohemia) going to MN.
1920 Fed Census lists Joseph & Rosalie Kapaun (72 & 70), immigrated 1873, living next door to William (41)and Ida (40) Kapaun and their children John (12)& Louella (9). Also next door are Victor (27) & Mabel Suess and their son Bernard (5 months). Next door to the Suess's are Frank (28) & Mary (25) Sexton and their son Francis (4 months?) and an orphan boy named Sylvester Drosier (11)
This Kapaun family lived in Janesvillle, Waseca County, MN as opposed to the previous Joseph & Rosa Kapaun, and their child Julius, that I found in Waterville, Le Seuer County, MN. That family did not immigrate until 1891. This family seems to hit your time lines more accurately with ages, immigration, etc.
If by chance this is the family you are looking for, I have found that I am also connected to them through Louella Kapaun Roessler.