Excellent back story, with a few hints thrown in to the main framework :-)
It seems to me that Bianca hits a good point... unless the 'Darcy family' in this story implies that it Elizabeth is not the one whom Darcy marries, or that Elizabeth forsakes her title?
But would that last possibility then implicate the end of the Dukedom, as she is the Duke's only heir, and if she takes Darcy's name, rather than Darcy taking Talbot as his (now THAT would be something!! Darcy giving up Darcy?!!), there would be no more Talbots?
Then again, she is not a Talbot now either, or is she?