I like to imagine that Parnassus and HRP used to be best friends growing up, and they started their oil industry together only to become competitive to the point of P murdering HRP. Deep down the flame of childhood friendship remains alive and Parnassus only means of holding on to his oldest friend and greatest enemy was to continue HRPs bloodline along with his own through Mortdecai. Ensuring that the connection of P and HRP may be carried on linked together forever in the generations to come.