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.
What a working and progressive lot they all are. No one is in a hurry, and everyone is doing his job. Someone is licking the pussy, someone is shoving in the mouth and everything is so fast and with feeling. A sea of passion and temperament. The blonde is smart, she knows what she's doing, she doesn't have to tell me anything. The guys are so hungry, as if they've been waiting and not having sex for half a year, they pant like steam engines.