San is secretly the son of Urdun-Mor and Abalach-Re; Urdun-Mor hadn't risen to full command yet, but his secret dalliance with the Grand Vizier also gave him the tools to rise to power. After determining her child San didn't have much power, Abalach-Re abandoned him to a noble house.
Now, Ushuch-Si knows who San is, and now can use that to the benefit of the Veiled Alliance. Neither he nor San has yet figured out that Urdun-Mor is the father.
After capturing San and the other children, using Usuch-Si's notes, Abalach Re buried the holding mine. Meanwhile, the party decided to infiltrate the mine, running into and murdering Urdun-Mor. San throughout decided to reject and semblance of their heritage.