What a fascinating, clever story this is! This is one of the reasons Beholder is such a terrific idea: the taking of characters mentioned only in passing and turning them into real flesh and blood and bone, the building of worlds so well-imagined that lead us beyond the glimpses given in the original with such perfection that we never for a minute doubt that they are true, and stories into which we sink without regard for time or place, only to blink muzzily at the clock when finished and think 'really?'. This one has all of that and delightfully so.
Your Kettleburn is an amazing man - resilient, perceptive, and yet a bit naive. Millicent is a brilliant match for him in every way. Her brusque entry into his life and the way she settles there effortlessly (to his everlasting astonishment) is wonderful. And Severus just breaks my heart. Silvanus' description of him is one I will long remember, it rings so true. The three of them together is singular magic, indeed.