Stories about the friendship between a mature woman and her best friend could be a great alternative. For example, they could go on adventures together, like traveling to new places, trying new hobbies such as painting or cooking classes. Their stories could involve how they support each other through difficult times, like when one of them loses a job or has a family problem.
No. Threesome sex stories involve sexual content which is inappropriate for public discussion. Such topics are private and often violate moral and ethical norms in a public setting.
No. Threesome sex stories are not appropriate for mainstream media as they involve sexual content which goes against the moral and ethical standards that mainstream media usually adheres to. It may also be considered offensive to a large number of the audience.
Mostly, they are fictional. Writers create these stories to appeal to certain fantasies. They might draw inspiration from general relationship dynamics and add a spicy threesome element to it. It's rare that we can be sure they are based on reality as people are not very open about such personal and often frowned - upon experiences in real life.