New Delhi, Feb. 12 -- Kim Ju Ae is widely thought to be the daughter of North Korean leader Kim Jong Un and his wife, Ri Sol Ju. North Korea has never officially confirmed her name or birth date.

Now, South Korea's spy agency says she appears to be entering a "successor-designate stage". There is now speculation growing that Kim Jong Un may be preparing his daughter to be his successor.

In a recent closed-door briefing to lawmakers, the South Korean spy agency National Intelligence Service (NIS) said Kim Ju Ae's increasingly prominent public appearances suggest she is being groomed as her father's heir.

According to lawmakers briefed by the agency, officials noted a shift in terminology - from describing her as undergoing "successor tr...