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.
For that matter, I'd rather have her in a 69 position, it'd be more interesting for both of us! By the way, she did a good job on the cock, too. Probably imagined herself as a cowgirl, and her shoes as spurs, which she used to ride the stallion! When she laid down on her side, her shoes disappeared, so the ride was over? Apparently the movie was filmed in several stages, and we naively believe that the male is so hardy and can fuck a lady for a long time and not cum!
I'd like to make out with a tattooed guy, send me his Instagram.