There are two ways to play the game I’m working on; Mom or Sister:
1. Incest route: your mom and sister will become more attracted to you, and eventually have a relationship with you.
2. Voyeur route: your mom and sister will be pushed away from you, but you will observe their sexual acts.
By increasing your mom or sister points, you will make them more attracted to you.
By decreasing your mom or sister points (going into the negatives), you will watch them become huge sluts for others.