Genetics
The Nuristani people's closest relation is to the Kalash people. Furthermore, they have very little genetic relation to neighbouring ethnic groups like Pashtuns and Kashmiris. This is because they have always remained isolated in the mountains which has led them to become a genetically isolated population. It is also speculated that Nurestani people are of different origin altogether assimilated in the region at some point of time in history.
Read more about this topic: Nuristani People