The dad is a badass monster hunter and Iris is definitely probably some kind of siren or other creature that attracts people and long lived. Maybe a vampire, some kind of demon, or succubus
Iris is really interesting to me - what is she? Many times it's said she's been in the mansion for a long time - is she a monster with long life span, or maybe a ghost? I thought that she's an earth-bound ghost (several references how she's been in the mansion for a long time), but in this chapter, Lip talks about going to the other town for shopping. She knows a lot about the mansion - it feels like she was there longer than the Blind family itself.