Parasitic twin

What do you think about this photo ? And what is this ?

Dx: Parasitic twin

Explanation :

Myrtle Corbin “Myrtle was able to control the limbs of her sister but was unable to use them for walking and she herself had a difficult time getting around as she was born with a clubbed foot. Technically, the ‘Four-Legged Woman’ only had one good, usable leg. Myrtle was a popular attraction with P.T. Barnum, and later with Ringling Bros. and Coney Island.