You could have a secret twin (but not the way you think)

While searching for a kidney donor, Karen Keegan stumbled upon a mystery. After undergoing genetic testing, it turned out that some of her cells had a completely different set of genes from the others. And this second set of genes belonged to her twin sister— who had never been born. How did this happen? Kayla Mandel Sheets explores the condition known as chimerism. [Directed by Luísa M H Copetti, Hype CG, narrated by Bethany Cutmore-Scott, music by Gabriel Maia].