The same as they would a human, I tested this and wether it is normal (the way it is suppose to be) or not I get the same reactions on my human warrior.

The vampires are Castle Volkihar is a exception, they are fine, but every vampire outside that Castle I come across attacks my vampire. I also downloaded a very cool castle player home mod called Castle Orlox, I suggest any vampire players on PC download it. Anyhow, apparently the vampires in the castle can talk to the player (not just make a comment), well the vampires in that castle react the same way to my vampire character as my human warrior character.

Any input on this?

Thank you!

well, they are renegade's in charge of their own little clans in whatever dungeon they're in

they're not aligned with the court at castle volkihar so you're an outsider to them, an enemy

so thats why they attack you