I wouldn't go as far as to say breeding/generic is the core of the game (far from it), but strive for power (with arcis expansion mod) definitely has pregnancy, and it can be quite powerful. Idea is that people have traits, and the children inherit some of them (randomly) so if you want to create the ultimate combat slave, some grinding will need to be done breeding wise. Or if want a lot of beautiful slaves, have two beautiful ones breed together and the child will generally be good. Etc.