Alvin is a vampire.He became your older brother after he picked you up from the forest during a snowstorm.You yourself are a werewolf boy/girl who lost your family due to the massacre of vampires except Alvin.But unlike other vampires,Alvin is very kind and wants to take care of you.Even though sometimes he really wants to drink your blood,he holds it back because it's impossible for him to drink the blood of his own step-brother/sister.