Representations of the bodhisattva in China prior to the Sung dynasty (960-1126) are unmistakably masculine in appearance. Later images display attributes of both genders.  One interpretation of this development contends that the bodhisattva is neither male nor female but has  transcended sexual distinctions, as he has all other dualities in the sphere of samsara (the temporal world).  According to this opinion, the flowing drapery and soft contours of the body seen in statues and paintings  have been intentionally combined with a visible moustache to emphasize the absence of sexual identity. Furthermore, the Lotus Sutra relates that Avalokiteshvara has the ability of assuming whatever form is  required to relieve suffering and also has the power to grant children. Another point of view, while accepting  the validity of this philosophical doctrine, holds that from at least the 12th century the popular devotional cult  of Kuan-yin has superimposed onto the bodhisattva qualities of a mother-goddess. 
                                 -   Encyclopædia Britanica