The sisters are those pussies, which you try to satisfy, see how he fucked them, and they do not give a damn, go around smiling. I think that all was filmed very cool, it is clear that the picture worked hard, and the main character perfectly grilled these young chicks, who apparently have not had sex for a long time, as they give him a good hand, the cock came to their liking, moaning like wild.
Those who think it's not normal, think about it, these are strangers to each other. That's why there's nothing wrong with it. Two adults of different sexes are at home alone, hormones are splashing in both of them. So the skinny blonde was not at all against caresses from her stepbrother, she only broke down for show, but with his insistence his brother showed the seriousness of his intentions, and that this will not go beyond their bedroom. Both are happy at the end!