Minecraft wiki entry for Before_Village_%26_Pillage, associated text: Residents of a village which has not yet reached its population cap will occasionally go into "love mode," indicated by animated hearts above their head (only visible if you have particle effects enabled, but still works even when you can't see it working). Much like with most animals, when two villagers are feeling "romantic" and can see each other, they will pathfind towards the other and "kiss" for a few seconds, after which a third, smaller ("baby") villager will spawn next to them. This new villager will be assigned a random profession (indicated by the style and color of its clothing), not necessarily the same as either parent.