...way to frame my question, already small in scope; my apologies. Your phrasing is much more to the point—should he do anything?—where the “he” is a concerned brother or other close male relative. Maybe not anything as dramatic as a duel or compelling a marriage, but some kind of upbraiding of Willoughby seems in order, and who else could do it? Perhaps it is an anachronistic thought, on my part, however, a wish that Willoughby not get away scot-free.

What set me off was the scene Andrew Davies added in S&S3, where Brandon confronts Willoughby on his intentions respecting Marianne. I’m not partial to the scene, because it implies more than is present in the novel, but it got me wondering whether there was something a properly concerned man in close relationship to Marianne might do along those lines, once the full scope of Willoughby’s misconduct is known. (Perhaps my question should have been ‘What would Brandon do?', if he was in close enough relationship to Marianne to take any step at all.)

I'm curious because it shows where society became interested in the private question, and where a man's conduct becomes so egregious as to elicit a social response. (I confess to confusing my question still further by musing that, if there were such a role for a brother, John would abdicate it.) You indicate that nothing could be expected absent a breach of social contract such as expectation of marriage, or an illegitimate child was involved, which makes sense. Societal conventions can't go marching in to set right every man who breaks any woman's heart, whereas the expectations involved in marriage, childhood, and the like mark a clear line.