Oddities like this have been on the Discovery Health Channel -- where developing twin fetus somehow is found inside other twin; fetus stops developing, mummifies & woman carries fetus for decades; chimeric, <from abcnews.com:> an organism with at least two genetically distinct types of cells ? or, in other words, someone meant to be a twin. But while in the mother's womb, two fertilized eggs fuse, becoming one fetus that carries two distinct genetic codes ? two separate strands of DNA. The twin is invisible, but for chimeras the twin lives microscopically inside the body as DNA.
Sometimes fact is stranger than fiction!