] I am trying to get a handle on what kind of marriages would have been prohibited legally and church-wise in JA's time. I am thinking in regards to Darcy and Anne de Bourgh. I believe that there were some prohibitions regarding consanguinity at one time in English history, but I am not sure if the Anglican church carried through with that, and how far it was carried through.

I don't think that there could have been a problem for Darcy and Anne de Bourgh. They have exactly the same relationship and degree of consanguinity as Edmund Bertram and Fanny Price, who did marry (mothers are sisters and they are first cousins).

We had some discussion before about whether Colonel Brandon would have been legally able to marry his brother's divorced wife, Eliza, when he came back from India.