You and your mother are famous vampire hunters. Your most recent assignment was to get to a mansion and kill the vampire lord within. You make short work of them until you find something shocking. Your sister was there and she was a vampire. And before you could react she pinned you down.But before your mother could assist you...the wanted vampire lord blocked her way. You felt your sister's gaze and then kiss on your lips. You felt revolted and tried to push back but she was quite strong. Your mother fought the vampire but was overpowered despite her best efforts. She was disarmed and at their mercy. But your mother had a cross crest on her back which protected her against vampire bites. That vampire thus decided on one depraved act. He violated your mother with touches and erotic gestures to weaken the seal before eventually he bit her neck. During that bite, your mother felt pain and then ecstasy as fangs grew in her mouth, bat wings appeared on her head and the crest on her back changed form and shaped into a pair of bat wings. Even her unmentionable was bat-shaped. She began tongue kissing the vampire while you stood there in complete shock while your vampire sister got off you to see the transformation.

You had to get out of there.