Twins reared apart do not exist

I was reading this post apocalyptic book, where the women were expected (but not required) to at some point make lots of babies, because they needed more babies to prevent from becoming extinct. That seemed sort of reasonable, especially because the author made a point of stating it wasn't required. He made a point that the women did all the things the men did and would not be forced to make babies if they didn't want to, but everyone saw it as a good thing if women did have babies. However it was also full of remarks like: Wow you're a good fighter, you must have children so we can have more good fighters. Which was kinda annoying.

Then there was a whole separate group of people, who had to limit their population size due to constrained resources. But they had access to a whole stock of frozen eggs and sperm and would use IVF to have children when they needed to. Also reasonable, with some caveats, but I'll allow it. But then they would look at the parents and select which eggs and sperm to use, in order to get the most useful additions to their population. So they would take good mathematicians and combine those if they wanted to have new good mathematicians. The main character was the child (via IVF) of one of the most famous and important generals and of course also very good at being in the air force. This is when my eugenics alarm was going off.

There was also this whole other group of human like aliens, and wouldn't you know it, genetics played a big role in their story as well. With eugenic themes all over.

I don't know if the author actually believed in eugenics or just didn't understand how genes work at all and went with his flawed understanding. But holy shit this book rubbed me the wrong way. I didn't finish it obviously and will probably avoid that author in the future.