It is not clear whether Jane & Lizzy have been any more diligent than their parents in directing the behavior of their younger sisters. I can't recall any specific instances but I'll try to look for evidence one way or the other. It's hard to imagine that Jane, who in the 21st century would be the head of her class in the school of social work, would not have attempted to improve them. It may be that they have tried but the younger sisters may have been impervious to their influence. Lydia in particular exudes a 'you're not the boss of me' attitude. Kitty has always seemed to me to simply follow the path of least resistance which would make Lydia's freewheeling fun more appealing than the older sisters' responsibility & decorum & amusement in wit. Mary, lacking the beauty of the other sisters tried to go to the extreme of accomplishment making herself ridiculous in that direction. There wouldn't me much they could do about that.