This happened to me at Sarethi Farm along with an Ancient Dragon and 2 other vampires hanging out on the porch, all at the same time.

The really strange thing was when i approached the group of vamps and the living vigilant they became hostile right as 1 of the vamps started to say something like "Hey Stranger!"
I think there could be more to this encounter but i just missed it because they preemptively went hostile.
Has anyone had this encounter play out differently ?