"Nuka is the first born and Zira took care of him with love but as the time went and Zira became a supporter of Scar and she got Kovu which looked like Scar, then she forgot Nuka and his inner strength.
His eyes were red, exactly like the eye colour of Zira's. Red like hatred. Jealousy. He is forgotten as a member of his family... and Scar has forgotten that he is the chosen one."