This was a custom
Virgin Mary hears some strange sounds in her house one night so she checks on her son, Jesus, to find him stroking his cock. She laughs at the size of her son's cock and tells him he shouldn't be playing with it. He nervously admits that he was playing with himself over her. He's heard screams of pleasure coming from her room at night and men leaving in the early hours of the morning.
Mary is appalled and pulls Jesus over her thighs to spank his ass. As she hits him, he tells him he's wrong for stroking his cock over his own mother and admits that she's been seeing other men at night. She tells him stories of how she used to be a whore before she met his father and that many men, monks, in particular would have their way with her one after another. Only, an angel told her to marry his father, Joseph, and now she's dissatisfied and bored. Because of this, this enjoy extramarital sex with all manner of men... and more.
Jesus still seems aroused so she decides it's time that she lets him know the truth about what she does to his Father. She lifts up her dress to reveal a huge strap on. She tells Jesus that for years she's been cuckolding and pegging Joseph because he's too pathetic to deal with her needs like a real man. She's decided that now, it's also Jesus' turn to learn all about her girl cock with his tiny shrimp dick.
She slides into her son's virgin arsehole and pegs him hard while encouraging him and telling him he's a good boy. He manages to take all of her length and cleans his juices off her strap on with his mouth. While she fucks him, she tells him more stories about Joseph and the men she sees at night. Finally, her strokes bring him to a dribbling orgasm and she goes to bed with him in her arms (her strap still in his arsehole).
They're awoken by Joseph coming home. He finds them like that and Mary simply wakes up and informs him that Jesus is a slut for her girl cock now too. Joseph is such a beta, all he can do is accept it.