I've managed to trace other grandparents back to their roots but Jacob is difficult. I have no knowledge of the German language nor what other names they might have used.
I've followed a few trees and at first I thought Jacob's wife was Johanna Charlotte. Paper trails lead me to believe it's Wilhelmina. Could his wife's name be a combination of the two? I'm not sure.
I found a ships list from Bremen with Jacob Knorr aboard. Evidently it is his service record in Germany? He would have been 26 years old. It's documented in the previous post.
I found Wilhelmina as head of house in 1870 with Christopher and Amelia in the household. Where's Jacob?
Jacob died in 1872 I thought. It's what his stone says. Perhaps he was in a care home? Remember, the previous census lists "Mene" as Jacob's wife so this would fit as a nickname for Wilhelmina. This census also lists a little girl named "Julie" Barcherding. Who's this?
The Amelia Borcherding Confusion
Fred and Matilda also had a daughter named "Amelia". It makes things confusing!
There is an Amelia Knorr who married Diedrich Borcharding on Sept. 22, 1859. Source: Adams County Court Records, Adams County, Illinois. Film # 1845384 -1845385.
Then Christopher also married a Borcharding. He married Wilhelmina Borcharding on Nov. 6, 1873. Source: Adams County Court Records, Adams County, Illinois. Film # 1845384 -1845385.
Maybe the brother and sister married siblings? I'm not sure. I still haven't found another instance of Julia Borcharding.
Last, Amelia Borcharding's death certificate lists Wilhelmina and Jacob Knorr as her parents. That makes the case of Wilhelmina being the children's mother. Jacob could have been married twice but I've found no sources to suggest that happened. Source for the death certificate:
"Idaho, Death Certificates, 1911-1937," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/FLT3-9YC : accessed 13 Feb 2013), Wilhelmina Nickeloid in entry for Amialia Borcherding, 26 Oct 1911.