why can't the homonculi get pregnant?
they can't copulate with humans as Wrath failed, but they never really specified what specifically prevents them beyond being homonculi if I remember correctly. assuming they all have genitals (which would track since Wrath attempted to have a child with his wife and failed, Greeds loves women which implies he has a lot of sex, and Prides fetal state had some), couldn't they at least have a child between each other?
in fmab, im not super sure how the souls work but maybe they could have sex, transfer one of the souls in their philosopher stones since they're still alive (and I'm sure one of these souls is a baby with a conceptualization of themselves not developed enough to reject), and imitate conception? envy has them embedded in her most powerful form so she at least can interact with them, even if it's not to the extent of hohenheim
2003 power system is a lot harder for me to grasp but from what I gathered, their sustenance (red rocks) were collected through a process involving pregnant women. they don't have souls but surely they could try to imitate the process and continuously sustain the child through the rocks? though this seems less likely since they would have to not only transmute but also redo the situation with Wrath, which would be hard
realistically they wouldn't but this ain't for them it's for me