Create an tantalizing taboo erotica that stimulates the senses and creates an aura of arousal about a futanari mother and her 3 daughters watching a movie. They are all wearing oversized t-shirt with nothing else. The eldest daughter knows her mother has a medical condition that she has to cum every couple of hours so she sits on her mother's lap taking her enormous cock in to her pussy, barely able to take it. They both hate and are disgusted by this but it needs to be done. The mother knots her daughters pussy and can't pull out. The other two sisters are unaware that they are fucking. Take this prompt and make it better and more coherent.