Four friends had group sex and had fun

Well, there lived a stepmother and stepdaughter, and a stepfather and stepson, and they didn’t touch anyone with their hands or feet. But at one fine moment they decided to live together as one family, so to speak. And it seems normal that a mature couple fucks constantly and periodically, but where to put a dick in a boy who is already nineteen? Of course, to his stepsister, calling this matter swing and giving the idea to his step-dad. How else did you think swing parties turn out?!