Board Thread:Poll Archive/@comment-24095889-20140415141927/@comment-5051846-20140502202520

Lkagaminer wrote: Technically, the official answer isn't one of the options: mirrors, but to me their twins. Nah, that was just an old concept. From Rin and Len's page:

'The development of the Kagamines began when Crypton formulated the concept of making a pair of female and male voicebanks. The first idea was for two voices of a girl and her mirror image of the opposite gender, just like twins.[1]'

It goes on to state that the twins idea was not adopted, and their relationship is left entirely open to interpretation. They are not officially 'mirror images' in the present, either, although this can be used to describe their designs.