Who is Bobby Hanser and Harold Koch from Drowning Ruth and what is their importance?

Bobby Hanser and Harold Koch are two of the wealthy young summer residents of Nagawaukee Lake, Hanser and Koch are, with Arthur Owens, members of the yacht club, racing their graceful A-boats. Imogene Lingren makes Ruth Neumann go to dances every Friday night in hopes of getting to know the boys better and, perhaps, get married. Bobby has a reputation for summer flings and appears to have a crush on Imogene. He shows off, taking the group out on his Chris Craft power boat after dances.