I would do it at a faster price with two outcomes, the first option is that the sister sits quietly and watches him jerk off, and after a few minutes she gets excited and starts jerking off through her panties, and her brother either watches this or helps, and the grandfather cums, and she cums, and then they run away. Scene Option 2: She makes some sounds and gets up, the grandfather gets up and looks, it seems she is not there, and then the grandfather opens the window and catches her, and then there are two scene options: the brother hid around the corner, and the grandfather caught her alone and told her to climb in there to him through the window, and then the brother watches this, as she shows the grandfather her breasts and ass in panties, and he jerks off to this, and the grandfather tries to somehow impale her on his penis, but he does not succeed, and he is satisfied with what he has and cums, and she gets out and leaves and is offended at her brother the whole way home. Or the second scene is that the grandfather catches them both and the grandfather looks at her naked, but the grandfather asks his brother to jerk him off and she jerks off and the grandfather admires her naked body and looks at her ass and her pussy and starts to paw her ass and twitches his finger to her pussy, she presses her knee against this and falls on her knees and in revenge they cum on her chest and then they go home like this, my thoughts were on this detailed scene and not like this author's, it's not clear why they stupidly went and all that