God help me, I'm letting my sims be Quiverfull.
I don't know how it started. First I installed Autonomous Casual Romance (ACR) which allows the sims to make romantic decisions without my guidance, and can choose to try to conceive without my directives. But it wasn't realistic enough. The female's fertility declined so rapidly that even with their best efforts to have a large family they were lucky to get 4 or 5 children before the sim equivalent to menopause. This just didn't mesh with the real world in which a woman devoted to childbearing could have 4 or 5 children in as many years. So I installed the Inteenimater so that my teen sims could marry and extend their breeding years.
Then I got sick of all the prosperity in my sim neighbourhood. Every other sim was mayor or chief of police and it made no sense. How can a town of 100 people have 10 mayors? So I decided to phase out the standard careers and employ the sims in home businesses. Households would set up a shop in their front rooms selling chairs or beds or cheesecakes while also being employed at someone else's store so that they had a guaranteed income.
So how did this lead to a quiverfull neighbourhood? I had several maternal deaths due to overworking pregnant sims in the home businesses, so I decided the mothers would not work. I had some very sweet sims that doted on their sim babies so much that I didn't want to restrict their efforts. Gradually this became a neighbourhood-wide movement and now the average number of children per family is 8. The neighbourhood is exploding and I might have to go on a rampage to thin out their ranks.