The father clearly raised his daughter - Dad is the main thing. You could always find support and encouragement from him. And to suck his cock is just a thank-you for having him. By pulling her on his cock, her father showed how much he trusts her and that secret will be with them now. And the chick did a great job - and daddy is happy and she's even closer to him now.
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.
She's a hell of a girl.