Well, in such a fanfiction, perhaps the rich man is desperate for an heir to carry on his family name and fortune. He chooses a particular man to impregnate his wife because he thinks that man has the right qualities. The story could then focus on the relationship between the wife and the man she is supposed to have a child with. They might start off as strangers but gradually develop a connection that is more than just about creating a baby. Meanwhile, the rich man watches from the sidelines, his jealousy and regret starting to surface as he realizes the implications of his request.
The rich man would likely interact with the other man in a somewhat business - like manner at first. He'd lay out his offer, explain the situation about his inability to have children. The other man might be hesitant or defiant. With the wife, the rich man would probably be more tender, trying to convince her it's for the best. The wife and the other man would start off awkwardly, not knowing how to approach the situation.
Infidelity could be a reason. If one partner cheats on the other, it often shatters the trust in the relationship, and the betrayed partner may decide that they can't continue. Also, communication breakdown. If they can't talk to each other about their problems, small issues can turn into big ones, and eventually, the man might feel that divorce is the only option.
One possible story could be that a man finds himself in an unexpected situation where he has feelings for a married woman. However, his sense of right and wrong makes him reluctant to take any actions that could lead to impregnating her. He might constantly struggle with his emotions, knowing that any step further would cross a major moral line and destroy the lives of those around him.
I'm not sure specifically which 'the rich man's wife story' you are referring to. There could be many stories with such a title. It might be about the relationship between a rich man and his wife, perhaps including their lifestyle, the challenges they face in their marriage due to wealth, or some sort of mystery or drama related to them.
I don't know who the author of 'the rich man's wife novel' is. There are so many novels out there and without more information, it's hard to determine the author.
I'm not sure specifically as I haven't read this exact novel. But generally, it might be about the life of a rich man's wife, perhaps her daily experiences, the challenges she faces in a wealthy but maybe complex social environment, and her relationships within the family and society.