He who stems from two mothers is the hero: the first birth makes him a mortal man, the second an immortal half-god. That is what all the hints in the story of the hero’s procreation are getting at.
Jung identifies second birth as the structural distinction between mortal and heroic existence, arising from the dual-mother motif in which a symbolic or supernatural mother confers the immortalizing transformation the biological mother cannot.
, Symbols of Transformation, 1952thesis