How about a freeuse scene with a step family, where sex with them is normalised and is something that's been going on and done for long time. Your stepmom and stepsister let you use them individually at any time throughout the day, while the other members talk to, interact with, encourage and discuss sex with both of you or go about their daily activities in the background as if it's normal. Like the below JAV series which I think is called a World where Sex is extremely easy. They also have other scenarios, like restaurant, classroom, office, etc, where the sex is just normalised as a regular open social act with extras acting normal in the background, doing mundane daily tasks, having conversations with each other or the viewer, etc. I think having believable and natural conversations with good extras would be the most important.
