Thank you. You're right, they don't make up for the ones lost. I like to say that for every child God kept for Himself, He gave me one to keep too, but I never forget that they are not the same children.
Part of my question came from wondering how long Darcy and Elizabeth were supposed to be married. He keeps saying that it's not that long, not that many years, but once you take into account the three lost at the beginning of their marriage, and then birth of three more, evidently old enough to be dancing around in a circle with their mother at that point, that's a good many years. So I read it again, and then it struck me that it might be Darcy imagining her with the children they lost. Since he's thinking about the prospect of her death at this point, it would make sense, and the way it's described is very dream-like. It's lovely either way, and I appreciate your willingness to leave some things ambiguous and for the individual understanding of the reader.