Several people have brought up if the little sister may have survived and may show up. If she did as an existing character who got amnesia and was raised by someone else my money would be on Polly. She's the right age, has dyed purple hair so she could be blond naturally, I think she has the right color eyes, and similar enough facial features going by the two pics in the character chart. But that could be down to just Daz models sometimes looking close to one another anyway or the quality of the head shots on the chart. Obviously, this is just speculation, but I think it could work and she'd be the best fit for a reveal as the missing little sister. The fact that she seems to be one of the few people not instantly drawn to the MC overtly is interesting too and could be because of a subconscious memory or something.
This is just tin foil talk of course...