Re: [BY DESIGN] Alien and normal sim never have alien babies

@comicsforever : This has always been this way, as far as I know. They are considered "alien hybrids" (not a broken kind of hybrid like other occult types who get mixed due to bugs). EDIT: Here's Carl's guide on aliens, but I can't vouch for its accuracy, so take it with a grain of salt: https://www.carls-sims-4-guide.com/lifestates/aliens.php

By the way, since you use mods, MCCC's Occult module allows you to make the game do as you expect with its pregnancy settings.