Gracie and Rosie Attard were born sharing a spine, bladder, and much of their circulatory system. Even if conjoined twins have separate organs, like two hearts or two lungs, the organs function in tandem. If one of the twins’ organs is much weaker, the other will compensate. Rosie’s heart was weak, so Gracie’s heart was pumping for both twins. But the strain of pumping so hard threatened to cause Gracie’s other major organs to fail. If Gracie’s organs failed, both twins would die.
