I'd probably date the photo to be mid 1860s; judging by the middle woman's clothing; a front darted bodice with bishop sleeves, peregrine shawl and lace 'house cap'. Both boys look to be in their 20s.
Could be postmortem - though I'm no expert (as we've already established

) . The boy on the left seems to be supporting her head, and from what I can make out the pupils of her eyes seem to be sort of rolled/glazed over (?) - which although this is not the best quality scan, you can still make out the pupils in the eyes of the boys (maybe she had light blue/grey eyes?).
The fingers do look very stiff and unnaturally posed - though I don't how they would have supported the book (bible maybe).