a shadowy, older sister, kim sol-song. purest of the pure. the only one among kim and siblings officially recognized by north korea's founder, kim il-sung. >> she has her finger on the pulse of the regime. she is helping mentoring themmen the relationship building that need to be done for kim jung-un. >> to consolidate, kim and his family run a ruthless net work of spies. north korea has operatives in the u.s. and south korea. to keep them from defecting, they use anchor children. >> an agent operating by him or herself in south korea would have their family left behind. north korea would use that as leverage. >> reporter: a north korean spy, told cnn his family was k cu