This allusion is taken form theNew History of the Tang Dynasty. There goes such a story that Emperor Li Longji (685-762) of the Tang Dynasty (618-907), also known as Tang Ming Huang, loved music very much. He himself could play several types of musical instruments and compose music as well. He selected hundreds of young men and maids of the honor, and settled them in a pear orchard in the capital, Chang'an (present-day Xi'an). The Emperor taught them in person to sing and play musical instruments. They were called "the emperor's pear orchard pupils." And the man of letters of the period, such as Li Bai, all wrote plays for the pear orchard.
Later, the term "Pear Orchard" came to refer to operatic circles, and opera performers were called "Pear Orchard pupils". If several generations in a family were opera performers, then the family was calledPear Orchard Family, such as Maestro Mei Lanfang's family -- the family was famous for playingDanroles and Mei Lanfang was of the third generation.