I understand. Sharing seems even less popular than cheating.

One dynamic I really like is one similar to oyakodon: Mother and Daughter, Big sister and little sister, teacher and student, babysitter and the "babysitted", or anything with an older, experienced woman corrupting an younger, more innocent girl, so you three can have fun together.
Other thing I really like is when the woman incentivize you to some taboo things, like a GF that likes incest and encourages the MC to do things with his family, each time more daring to the other, starting with roleplay, then going to spying them, using their used panties, making them taste you cum in secret until you finally get to touch and fuck them.
I really like when the woman is the more pervy one...