Yea it requires you being defeated by a Goblin (Female) and then failing 4 endurance checks. Once she lays her eggs you'll need to be a bottom to one of the 3. Centaur/Harpy/Werewolf. Then wander around awhile and you'll get an "Encounter" screen, which will be the birth. I'd recommended just saving after the eggs then finding one of the three and then reloading after each birth just to expedite the process.