I got 2 more of eternally carrying mothers (and those 2 were gonna be JOATs) and neither of them were Grant Youthed (can be Grant Youthed's kids although) so I'm quite sure that if father is Grant Youthed then mother carries baby/babies forever (before dies). I de-aged all my curent JOATs

Its very hard to get JOAT during 1 lifetime so those eternally carrying mothers (mine are Esteemed Elders who have mastered Devotion) really messes game.