[No fixed couple + many children + the leads may not be chaste before they get together, but once they do, they're devoted only to each other, whether in ancient or modern times]
Across the three thousand worlds, there is a kind of System called the Wish System. As long as you have enough merit, it can grant your wish.
It sounds impressive, but quick transmigration agent Bai Qingqing has a question: Why is everyone who comes to me to make a wish asking me to have their babies?
System Weiyangyang: Qingqing, sob... my heroine System attributes...
Bai Qingqing immediately changes her tune: There, there, don't cry. I'll earn points and get you a replacement. What's the big deal about having babies? Have you ever seen anyone on land who can reproduce better than rabbits?
Weiyangyang, matter-of-factly: Mice...
Bai Qingqing: That's practically the same thing, okay? Now be good and stop talking. Read more books, learn some things, and use that knowledge to soak up the water in your brain. Don't be so silly, getting tricked and even paying extra for the privilege.
With that, she starts taking clients...
Client One: Brooding Emperor. “I'm a man, but I have to admit I can't perform.”
Bai Qingqing: So, what's your wish?
Brooding Emperor: “Have a child for me, and I'll give you all the merit.”
Bai Qingqing: Deal. Leave it to me.
She takes out a mortar and pestle, grabs a handful from here and another from there, and starts grinding away. That night, she becomes a bride, and the following year, a mother.
Client Two: Mighty General. “My fiancée broke off our engagement, saying I couldn't perform. Ever since, I really haven't been able to.”
Bai Qingqing: Easy. I'll have triplets and serve that sweet little white flower some face-slapping!
Everyone: The general can perform, and then some. Respect!
To be continued...