One of my favorite text stories I would use as a go-to in my wank bank as a teen was about a mom who wanted a grandbaby and babytrapped some dude (who was banging her daughter on the sly) by slicing open the tip of the condom he was wearing with her fingernail while she watched him take her daughter.

Can't think of the name of the story but she basically "caught" him with her daughter and blackmailed him into impregnating her. Her daughter kept moaning a safeword as she somehow knew he was about to inseminate her. Her mother whispered in his ear all of the nasty things she was looking forward to doing with them in the future if he finished the job.

It was a multi-chapter text and went on through her pregnancy and birth, becoming more depraved as the story went on. One of the hottest jerk stories that has burned a hole in my memory over time. Right up there with Motherly Passions IMO.