Very interesting, Robbin, thank you.

It's fun to look at the different pairs of sisters in Austen and consider that she was one herself. Is it too farfetched or a justified supposition that Jane was the "wild" one, more inclined to do what she preferred and Cassandra the calm, wellbehaved and orderly one who conversed with people instead of observing them (and taking notes for further contemplation and use)?

As you have said, in the three pairs in S&S there is one who's at least seemingly more in control and one less able - or in Marianne's case less inclined? - to handle the society about her in a mature way. [Although she improves as the novel progresses.]

I've not been around to follow every week of the GR and so don't know whether you have mentioned the possible impact of which place among the siblings a child/girl occupies.(Sorry if this is a convoluted sentence).
Perhaps there is inherent danger in the indulgence of a loving mother? And a tendency towards a more responsible behaviour in the eldest child?

Marianne is the younger one of the Dashwood sisters(sorry Margaret, you are still a child), her mother's favourite and also the one most like Mrs Dashwood.
Deeming from their families Charlotte seems to be the younger sister (more recently married and having her first child)and she certainly resembles Mrs Jennings more than Lady Middleton does.
Robert Ferrars is the younger brother and his mother's darling no matter how badly he behaves. And in their characters there seems to be a horrible likeness. Silly mercenary and without any honourable concern for their son/brother.

Is Willoughby an only child? An orphan at an early age? Are the Steele sisters left to fend for themselves very early? Who loved them?