Alys Caithness

Assumed to be a daughter of Clytemnestra "Fanny" Glitters, Alys Caithness was released at birth to the custody of her father, Scott Caithness, a visual artist of some repute in Dartwright. As Fanny had only been back to Dartwright once after the birth, she has little knowledge of (and at the time, little care for) the disposition of the child.
Alys' mother is a topiary artist, whom Fanny dismisses blithely as a gardener or hedge-trimmer. The two do not get on, with Fanny nearly slicing her to shreds at their last meeting. 
Vega Spritzer's message from Eldath suggests that when the Illinsi came to Dartwright, Scott held up under questioning (questioning by the Illinsi? how?) but that Alys' wicked stepmother spilled the beans about the child (now a teenager of some 13 or 14 years) having been sent to the Red Osprey Keep for religious instruction.  Such a move would make some sense at the upper tiers of Tenth society, where the clergy occupy a higher social caste even than artists.  Any promotion between castes in that society is a long shot, but perhaps one the Caithness family -- longstanding, very well respected members of the immediately subordinate class of artists -- were willing to take.
The fate of all three(?) members of the Caithness family is unclear, though Eldath's reference to a third star in the sky seems to portend nothing positive for Scott.