What does Katie recall Miss Vernon telling her about Jackson Pye's sons and her intentions toward one of them?

In Chapter 10, Katie relates the story of the Pyes as she learned it while weeding Miss Vernon's garden in high school. Miss Vernon told Katie how each of Jackson Pye's sons left, one at a time, until finally only Henry and Art were left. Miss Vernon and her sister had their hearts set on marrying Henry and Art, of making a life together in the Pye farmhouse, but that was not meant to be.