In 1895 , surgeon J. W. Ballantyne considered the case of the Biddenden Maids from a teratological perspective . He suggested that they had in fact been pygopagus ( twins joined at the pelvis ) . Pygopagus twins are known to put their arms around each other 's shoulders when walking , and Ballantyne suggested that this accounted for their apparently being joined at the shoulders in drawings . The pygopagus Millie and Christine McCoy had lived in Britain for a short time before going on to a successful singing career in the United States , and it was known from their case that such twins were capable of surviving to adulthood .