Riatavin is not in Tethyr, it has been too long :] ...well let me think a little more on it.
My other thought was they are from just outside of Zazesspur after his father retired from the military. Their villa sits at the base of the purple hills. His father is a loyalist so he may be involved in one of the underground groups but has yet to involve Molgrin.
He has ideas of what might be going on though and has seen a lot of "army" officers coming and going.
I can work more of this kind of stuff into his background if I end up being selected. Good luck with the selection process.