Daughter gets reunited with her biological parents

Its been almost 20 years since Mona and Rock made the most difficult decision of their lives and gave up their baby for adoption. And now here she is, sitting in front of them, meeting her biological parents for the first time. They explain to their daughter why they had to give her up; their household was a volatile place and their parents didn't approve of them being together since they are brother and sister. So they gave up their baby for adoption so that she would grow up in a loving, safe household. Lily is just now finding out that her parents are also siblings, and she is horrified and shocked by this news. She tries to work it out in her head, how this could be possible. And even though her parents are obviously in a loving, happy relationship, Lily is just repulsed by her biological family. Her parents start making out in front of her, and then Mona invites her to fuck. Lily hesitates, unsure if she heard her correctly. But she did. Then she thinks about it. Why not? They fuck all the time and even had a together and she turned out fine. Okay, she says, a little unsure, but shes willing to try it. Mona shows her long lost daughter how she likes to suck her dads dick. He is her big brother after all, so shes really good at it. The girls suck his cock together and Lily really starts to get into it. The three move to the bed, where they really show their family values. They fuck in a variety of positions, switching off sucking Rocks dick, Mona eating her daughter out as she sits on her face while Rock fucks her. They fuck all over the room until Rock cums on his daughters tits.