He married his first cousin Lucinda Fanning, and they had one child, a son, Richard Harrison Fanning. Jacob appears on a Dade County, Missouri Census with the family of Thomas and Harriet Lydia Emmons Fanning. He appears to be a son in this family but actually was a nephew who came to live with Thomas and "Lyddie" after his father died.
There are a couple of stories about Jacob and Lucinda. During the Civil War the armies of both North and South would raid the neighboring farms. Jacob and Lucinda took no sides. If they heard horses coming Jacob would go into the fields with a gun while Lucinda would hold up a lantern lighting the approaching riders. Jacob then fired a warning shot if it was the wrong people.
Once Jacob was in prison, and Lucinda visited him, taking home his laundry in a laundry bag. In the winter when the ground and the river froze, she went to visit him and brought him home in the laundry bag instead of his clothes, dragging him across the ice.
Jacob was alive in 1864 when he signed an affidavit for probate of Thomas Fanning's will. It is not known when Jacob died nor the cause of his death. Lucinda remarried in 1869 to railroad man John Ira Hoskins.