I don't have any sources rn but being raised as an Arab muslim I know that one of the """"porphecies""" of end times is that the child of a salve becomes her master, so maybe only males were castrated but females definitely reproduced?

As for recent times, I know whole afro-families that were enslaved to the natives of my village (in Asir, southwest modern day Saudi). Of course today they are free, but my grand father used to tell me about house of xyz how they were our personal slave family and they were very loyal (gross I know), the impression I got being that slaves married slaves and the offsprings were automatically slaves to the same owner.