Psyoptipickle has an interesting post on twins.
There’s something magical about identical twins. True marvels of nature. It’s that perfection to their mirroring that makes them so mind-boggling. But alas these curiosities of our cosmos are also magnets for the criminally insane. The Nazis were obsessed with them. Dr Mengele, the mad Auschwitz shrink was infamous for his evil experiments on twins in his “care”. Or so the story goes.