I think I have found Bette and Bettye/Bettje Jochums in the 1870 census for Marshall County, IL:
Bet Yocum farmer age 27 born Prussia Bettie age 25 born Prussia Mary born Dec 1869 Illinois
There is a Mary Jochums Meierhofer, born 18 Dec 1869 died 15 May 1941 Woodford Co., IL, buried in the Woodford Cem in Minonk where both Bette and Bettje are buried.
Bettje apparently died in April, 1880 in childbirth. I believe she is listed in the 1880 Mortality schedule for Woodford County as Bettie Johannes, died Apr 1880 in childbirth, and an unnamed infant girl Johannes died Apr 1880 is listed with her.
I cannot find Bette and the older children in the 1880 census, but by 1895 they are living in O'Brien County, Iowa, and then by 1920 he has returned to Minonk to live with his sister Alste.
There is a Claussen family in the 1870 census living in Minonk, Alon/Aton Claussen born about 1798 Hanover, with (presumed) wife Onka also born 1798 Hanover, and Herman born 1828, Tinka born 1835, Derk born 1856 and Hinke born 1862, all born Hanover. Buried in Woodford Cem there are also Tatje Claussen Jochums 1849-1934 born Lower Saxony Niedersachsen, Germany, parents unknown according to the IL Death Index and her husband John T Jochums, born 1848 Germany, parents Jochum and Mary Johnson Jochums. I would suspect that this might be a case of sisters Bettje and Tatje marrying brothers Bette and John. There are no marriages from either Woodford or Marshall County included in the IL Sec of State's online marriage index, but you could write to the clerk's office in the Woodford County courthouse and ask them to search for a license.
The Woodford Cemetery memorials on findagrave.com were all created by Amy Robbins-Tjaden. You might try contacting her through findagrave to see if she has any more information on this family.