Responses
Their goal was to prevent Feng from having a kid, because of the inheritance thing.
What they didn't know was the egg they stole wasn't Feng's, so they fucked up. Though the latest chapters in the raw didn't discuss it anymore. They kinda focused on the relationship of Feng and Yiyi, and Rourou meeting the grandpa, and grandpa handing the company over to Feng (because he found out about the bad intention of his other two children!).
So even if someone did the fertilized egg what would they do with it? Put it inside a women and make her have a baby that is technically stolen. If they even tried to get money out of that situation it doesn't make sense. Either they sell the child or they blackmail him for money for the child that they stole.