Who is Bobbie and Katherine from Neither Wolf nor Dog: On Forgotten Roads with an Indian Elder and what is their importance?

Bobbie and Katherine are the names of Danelle's mom and dad. Bobbie was Dan's son with "some white-churchy social worker", who left to go back East because she couldn't take the prairie. Bobbie had a hard time as a half-breed, meaning he had a white mother and Indian father. Katherine was Annie's daughter, presumably with Grandpa. Bobbie married Annie's daughter, Katherine, who was Danelle's mother, with Bobbie being her dad. Bobbie went to Haskell College and was going to write a book that would become a bridge between his parents, Grandpa Dan, and Dan's white ex-wife. Presumably, Bobbie's letters from Haskell College that Dan saved were in the shoebox Dan was going to use when he asked Nerburn to help him write a book.The reservation police said they were killed in an auto accident but there were unexplained bullet holes in their bodies.