You're actually not the only one.
But you, and all the others that think so, are incorrect.
My very first post on this forum (4 years ago, ah, so nostalgic):
The other, more plausible theory, is that Bianca's mom is the girl in the middle (can't remember her name and I can't be fucked looking it up). They have the same necklace, both redheads, but who knows.
What we do know is that Jill isn't his aunt for two reasons:
- The link above describes how it doesn't line up; and
- if the game included incest, Patreon would not allow it on their site, and that would cost the developer 10s if not 100s of thousands a month in Patreon subscriptions. He's not gonna risk that just so people can jerk off to the thought of fucking their own family...
So no, not an aunt, sister, mother, brother or any other fucker (Lock Stock reference for those who love that movie).