Unnatural Arrangement

Ever since his parents passed away years ago, Nate (Parker Ambrose) has been living under the care of Henry (Derek Kage). Even though Henry is only related to Nate by marriage, they've been a happy family. But Henry has recently married Bridget (Ivy Ireland), and she is already making disruptive changes to the house. Nate resents this, but Henry urges Nate to make Bridget feel welcome.
However, one day Nate comes home to a real shock... Henry and Bridget are having sex in the kitchen, and they don't stop even when they see him! Henry reveals that he and Bridget are in a free-use relationship, so Nate will have to get used to it. Nate is disgusted at first, but as he prepares a snack and makes conversation with the couple during the ongoing sex, he finds himself becoming intrigued by the idea of free-use. Henry and Bridget notice, and say Nate can be part of the free-use arrangement from now on. They come together for a twisted family threesome, including double-penetration.