https://www.nytimes.com/1985/07/21/magazine/what-made-this-man-mengele.html
Yet most of the twins were safe, under the protection of Mengele, and much of the time he treated them lovingly. According to an inmate doctor, Mengele in his contacts with the children was as gentle as a father, talking to them and patting them on the head in a loving way. He could be playful, jumping about to please them. The twin children frequently called him Uncle Pepi. Sometimes, though, as the inmate doctor reported, Mengele would bring some gypsy twins sweets and invite them for a ride in his car, which turned out to be a little drive with Uncle Pepi, to the gas chamber.