Who is Fonsiba, and why does Ike feel the need to track her down?

After reading the slavery ledgers from the plantation, Ike feels the need to track down his relatives, including his cousins, and given them what he believes to be their rightful inheritance. He tracks down one of his second-cousins, Fonsiba, in Arkansas where she has settled down with her Union-Army husband. Ike sets up a three-dollar a month pension for Fonsiba and her family, and then returns to Mississippi.