(Trigger Warning: This post involves references to rape and non-consensual sexual acts in SF erotica and erotic sci-fi romance.)
Breeder erotica is alive and well and has been around for many years. It's particularly a staple of SF/horror erotica. It also makes regular appearances in erotic sci-fi romance. A cursory check of Listopias on Goodreads will turn up packed-to-the-gills lists of “Mars Needs Women” and “impregnation” stories.
Breeder SFRs typically involve heroines who are captured for often non-consensual, forced impregnation (or at least that's the initial intention). These stories typically include graphic sex, dark content, and some romance. One of the more popular premises is that an alien species has lost all or most of its childbearing women and so require a fertile, compatible species in order to survive.
In a science fiction/SF erotica tale, it's a pretty horrific situation since women (usually from Earth) are kidnapped, raped, imprisoned, and forced to bear children. To what extent does adding a romance change or transform such stories?
Cara Bristol's Breeder is pretty transparent about its dark content. The society is one in which patriarchy runs amok. Men rule the world and they view women as subhuman.