This scenario is used too often, that the stepdad "suddenly" finds his wife's daughter attractive. Why not portray something more realistic, namely that he was attracted to her the moment he saw her, that he pictures her in his mind when he fucks her mom, that for months he's been masturbating on her bwd when he's alone in the house, with her panties wrapped around his cock. When he cums in them sometimes he hides them amongst the other clothing in the laundry basket, but occasionally he puts the soiled panties back in her drawer, knowing she will find them and wonder why they're sticky...