How I love this swingers fun! And the girls this time, all model-looking. Good for the men! By the way, did you notice how all three girls were hanging around the black guy? They saw that he had the biggest dick and immediately surrounded him with their attention. I would have felt sorry for my wife, but I would have loved to participate.
Well, half-brothers and half-sisters are not related at all, so it can't be considered something bad or immoral. It's no surprise that an adult guy and girl, with no regular sexual partners and almost daily being around each other, suddenly felt attracted on a sexual level to each other. Considering that the girl liked it (the guy then no question), I think they will continue to practice this kind of thing from time to time.