I'm not here to add details on the origin of the Shahs, just trying to make it more complex like a typical Nepali. It will be hard to trace the origin with pinpoint accuracy without historical artifacts and records. Some say they are Rajput, some say Iranian Muslim since they had Shah Kings too, some say they are mixed with kiratees. Whatever, it doe snot matter, they are all gone now.
Kanchu...Kahn means brother, where did you exactly get that from? It sounds more like "Kaan" like our ears...