Magistrate is sneered at because, though his father, Lord Kim, is a high-ranking noble and he himself is recorded on the Kim family register, his mother was a slave, not even a concubine, and the daughter of a traitor. Her father, Lord Seo, *was* a high-ranking noble but was framed and died with the rest of his family. IIRC his wife also died at the same time, and only the daughter was left alive/ allowed to remain alive. We know this from the mother's own words: 'This is the day your grandmother and grandfather died, and all your uncles.'
Now I don't know if generational executions, that charming custom, involved women as well-- was Grandmother executed with her husband, or did she kill herself? Was the family in fact executed, or was it an attack on their palace and a slaughter? I don't even know if Grandmother was the main consort or not-- I may just be assuming this because she dies with the lord. My assumption was that daughter was reduced to slave rank following her father's disgrace and was once legitimate. If she was a slave from birth, why does she have the manners and language of a lady, as noted by the servants at the house where she asks to be allowed to serve in the kitchens.
But mostly what puzzles me is the fact that our magistrate was born before his grandfather's disgrace and death, because his servant/ slave was given to him by his maternal grandfather. If mother is slave by birth, how come she's having liaisons with some other noble? If she's legitimate, even more How Come. The scenario makes sense if Lord Kim takes her in after the disgrace of her family, but he didn't. I am hoping for enlightenment but don't think I'm going to get it.