Who is Jacob Calvino from Brother Odd and what is their importance?

Jacob is in his mid twenties and afflicted with a disease similar to Down's Syndrome. A misshapen head and jaw, and one eye lower than the other make his face and head seem somewhat lopsided, but he lacks the flat nose usually characteristic of Down's children. He has a stocky build, a thick neck, and his left temple is convex, while his right temple is concave. His heavy shoulders hunch over one of many drawings, all of the same woman. His mother was John Heineman's fiance in the days when he was just becoming well known for his scientific mind.