Adam and Pinar
They were a Turkish contortion duo that performed during the first world war, a boy and a girl, not related, their trainer set them up. They were both backbenders and were both around 17 during their performing years. Pinar (the girl) and Adam (the boy) performed for prominent officers during the war and judging by descriptions, were incredibly good.
They became super close friends since they were set up at the age of 12, but were never romantically involved for a specific reason. After the war was done, so was Adam's career after he got jailed. Apparently, Pinar would keep visiting him in a costume to practice with him for several years after his imprisonment.
Thanks to Filter-GX for the information and this description!