Phi-Phi
The Shan tribe of Thailand has a powerful spirit that permanently lives within the person, transforming them into witch.
The witch has many powers including shape-shifting into animals.
Phi Phu is passed down through family. Its also contagious, if you share too many meals with a phi-phi, you can be infected. Marrying outside the tribe will bring a Phi Phu into the family.
Phi Phi can send human doubles away. As long as a phi-phi obeys social expectations and laws, it will be accepted. The phi phy is unfortuanate, but not malevolent. The only way to exorcise a phi-phi from a person is that person becoming an ordained Buddhist monk.
Mari Wells 
Nice that they have social conventions and a means of accepting magical beings.
There are a few folk lore vampires that were accepted into the community as long as they “fed” far away.
At last I think I understand what happened to my mother in law!
Shhhh. You don’t want her to know you know. You never know what she may plan if she knows you know, you know. 😉