"Why should the Kurds let him go near Wassmuss?
Unless they return him safely to us we can execute their hostages; they will run no risk of Wassmuss playing tricks with Gooja Singh.

Besides, from what I can learn and guess from what the Kurds say, this Wassmuss is to all intents and purposes a prisoner.
Another tribe of Kurds, pretending, to protect him, keep him very closely guarded.

The best he can do is to play off one tribe against another.

Our friend said Wassmuss holds his brother for hostage, but I think the fact is the other tribe holds him and Wassmuss gets the blame.

I suspect they held our friend's brother as security for the gold he is to meet and escort back.