Maybe she is testing the boundaries with you Josh, by mentioning that she would like to have baby with them and you will help to bring them up. Is that something you would want to do?
If not, then you should say this to your wife. It is the same with multiple lovers. It sounds like she is really expanding the limits of your flr.
As James and Tempest have said communication is key and you shouldn’t be forced to go along with anything you are not comfortable with. Everyone is different, I see an flr as pleasing my queen no matter what she asks.