Well apparently the girl likes to ride on a big dick of her lover, see how she goes along, and even then to a greater extent he fucks her, not she on it, although what difference does it make, because the change of places do not change the sum, especially in such a delicate matter. They obviously fucked in the glory, and both received an unreal pleasure, it seems to me, and I think the repetition is not far off.
The sister is really uninhibited. Judging by the reaction of his brother and his unwillingness to break away from the game, his sister is already bored with him to say the least.