For the 'Rose Family Vampire Panic Fanfiction', the main characters could start with the Rose family twins. They are very different in nature. One is more introverted and the other is outgoing. The introverted twin might have a special ability that they are unaware of at first, which could be crucial in dealing with the vampires. Then there's the family's crazy aunt who has always been interested in the occult and she might have some knowledge about the vampires that she shares with the family. Also, a vampire hunter who initially targets the Rose family but then realizes they are on the same side against some really bad vampires could be a main character.
The Rose family's eldest son, James Rose, could be a central character. He's a bit of a rebel and his recklessness might get the family into trouble or it could be the key to their survival during the vampire panic. Another character could be the family's matriarch, Mrs. Rose. She has a kind heart but also a firm will and she uses her wisdom to guide the family. And there could be a mysterious stranger who shows up during the panic and has a connection to the vampires but also becomes an ally to the Rose family.