You CAN save sims
No, you can save households. You can't save Sims on their own for you to import into other households.
and you CAN make twins.
No, you can make a clone of a Sim with randomly generated clothes, hair, makeup, etc. You can't just straight-up duplicate a Sim.
You can't have the same person develop the same game all the time, even COD gives itself to different developers each year and It changes a bit year by year.
Call of Duty has had three developers over the course of 11 years and has produced 11 games in the franchise; nine of which were developed by the same company. The Sims was developed by one company over the course of 14 years and only has four games in the franchise. I don't see your logic.