What’s more rare than identical twins? Mono mono identical twins, the term for when twin babies have not only split from the same egg, they share the same placenta and amniotic sac while they’re in the womb. Incredible already, right? Well, just wait until you hear the story of Sarah Thistlehwaite, a mother carrying mono mono twins, and learn what the twins were doing when they entered the world. CNN shares the sweet story.