My mom Sim was pregnant every day of the challenge. Both parents got the fertility reward during the first pregnancy, and they used the fertility elixir once, and always had at least two spaces open for children when they conceived. Still, in both my practice and actual, they ended up with only two sets of twins. Did those of you that got more twins do anything else that you think affected this?
My main strategy was to give all the fastest aspirations to the kids. When they moved out, I spent all their remaining points on moodlet solvers, even though they were rarely needed. This is because I kept my bestselling author Sim kid around for most of the challenge after he completed his aspiration, in order to write books of life for everyone. There was always enough room in the house for him to stay and for the possibility of twins until near the end when I had a multiple career aspirations going at once, and some other toughies.
I had the kids do some of the faster aspirations at the beginning, since they didn't have moodlet solvers or books of life yet, but saved the very fastest for the end, so that they could be completed in a hurry before the kids moved out. I decided that Mansion Baron and Soulmate were the two fastest, so I saved these for the final birth. Only one kid ended up being born, so he did Mansion Baron. If no skill was very necessary for the aspiration that the kids earned, they would max herbalism as teens since it's the fastest. If the parents could help prepare for an aspiration, they would. For example, the mother had a garden of excellent+ plants in need of evolution ready for a child to do the Freelance Botanist aspiration, and the father completed a collection of postcards so a child would already have a complete collection for The Curator. The father also got the mentor perk and mentored kids in handiness and guitar. The kids did social butterfly for the most part unless they were going to be maxing creative skill. The only exceptions were that the one doing Bodybuilder did Rambunctious Scamp, and the ones doing Nerd Brain and Computer Whiz did Whiz Kid.
I found Social Butterfly to be the fastest of the childhood aspirations, and would help the kids out with it in two ways. If there weren't enough children in the neighborhood, I would have the mom or dad select file for adoption on the computer but then cancel it, and this would put the kids that would have been adopted into "not in this world" with a parent so that they could be found on the street. Also, if it was late at night and the kid needed to make people or make friends, one of the parents would throw a party so that the kid could meet or befriend those people.
Congratulations LenaLJ on your win! Also congratulations to Christinal3106, who was winning all the way until the end, and then lost by one point.
Edit: I forgot to add that the only kids that every went to school were the ones doing Whiz Kid. The rest requested a vacation day every day. Most of them selected Renaissance Sim when againg up for the quick learner bonus, unless they were leveling a creative skill and wanted the Muser bonus. I couldn't believe how fast a Sim with morning Sim/Night Owl currently active, Muser, and the bonus from Artistic Prodigy could level cooking! He get more than two levels from cooking a single meal.