Interesting bit of backstory on the two of them. I like how you covered something not mentioned in the main storyline, which is the details of how they met.

Oh Kastor and Mikah, Mikah and Kastor... this is a wonderful little insight into their past, and that second to last line, the one that went:
"He glanced up, and saw Kastor [...] smiling the sort of cynical smile one does when one hopes and hoping hurts."
actually nearly made me cry with the poetic melancholy of it all.
Wonderful, as ever.

This adds a beautiful depth to Mikah stealing Kastor's earring at the beginning of the first book. Lovely. :)