This is an interesting story, and unusual in the way you've set it out as a list rather than an actual story. I found it intriguing, although I have to admit I'm not sure it would have held my interest if it had been much longer. I'm wondering if a few more passages with some dialogue interspersed in the reminiscences would have helped as well.
What I did like was that this was a lovely tale of courtship and slow burning love that led to a very real love between your protagonists.
I did notice the odd mistake They never considered themselves great lovers of children, but they find that Sirius, Lycoris and Regulus a bright stars in often bleak lives. I think you mean Arcturus - not Sirius when you're listing their children, and instead of 'a' you should put 'are' (simple typo - excuseable) Also there were parts that seemed almost too modern for this pairing Sure, they’re nowhere near old, That sounds a too informal for a nineteenth century couple, but I understand the sentiment totally.
I was slightly confused by the end. Why can Hesper die in peace? It didn't sound as if Sirius was particulalrly tempestuous. From the story you've written, it sounds as if she can die 'happy' knowing that she'll be reunited with him (although that's phrased in a very cliched manner, but I'm sure you get my drift).
Did like this unusual story, though ~Carole~