I haven't played any that are quite what you're saying. Hopefully someone else knows of something because it sounds great to me. A few that have at least a little bit of stuff you might like:
High-Rise Climb - Your girlfriend's sister can move in with the two of you and you can pursue her.
My Sweet Neighbors - You start dating your neighbor and can also go after her daughter. Abandoned, but there is a pretty fair amount of content there still.
Triangle - She's more like your girlfriend's adoptive daughter and it's definitely more romance than corruption but you might like it.