It's clear that JA felt a wife had a marked effect on her husband's character (something I'm not so optimistic about, myself! :-). We are told that "had (John) married a more amiable woman, he might have been made still more respectable than he was; he might even have been made amiable himself; for he was very young when he married, and very fond of his wife." In "Persuasion", Lady Russell is convinced that if Charles Musgrove had married Anne Elliot instead of Mary, *he* would have become a better man.

As for John Dashwood, I always got the feeling (on no particular evidence except that of JA's own life) that he did *not* spend a lot of time with his step-mother and half-sisters growing up, probably because of being away at school, and that there was always a certain emotional distance between them, at least on his side.