February 14, 2017 9:17 AM EST

North Korean leader Kim Jong Un’s estranged half-brother Kim Jong Nam has been killed in Malaysia, South Korean government sources confirmed Tuesday.

The country’s cable television network TV Chosun reported that Kim Jong Nam died after he was jabbed by a poisoned needle at Kuala Lumpur airport by two women still at large, who are believed to be North Korean operatives.

Police confirmed to Reuters that an unidentified North Korean man died en route to the hospital from Kuala Lumpur airport on Monday. Abdul Aziz Ali, police chief for the Sepang district, said the man’s identity had not been verified. Local and other media is indicating that the deceased man is Kim Jong Nam, Kim Jong Un’s older brother.

Here are some of the key things to know about the exiled scion of the Kim dynasty:

Who was Kim Jong Nam?

Born in 1971, he was the eldest son of North Korean dictator Kim Jong Il. His mother was Song Hye Rim, a North Korean actress who was initially Kim Jong Il’s secret mistress.

Sung Hae Rang, Kim Jong Nam’s aunt, helped raise him along with her own children — a son and a daughter — before defecting in 1982. When he was around 27 years old, he began working at the Ministry of Public Security.

As the eldest son, why did Kim not become leader?

He was originally thought of as the heir apparent to the Hermit Kingdom. However, in 2001 he fell out of favor after he was seized by Japanese authorities at Narita airport, accompanied by a boy identified as his son, for trying to enter the country on a forged Dominican Republic passport.

Kim, who held senior positions within the North Korean government at the time, allegedly told police that he simply wanted to visit Tokyo Disneyland, ahead of being deported to China, TIME reported in 2011. The incident, coupled with the rumored defection of Kim’s mother (she died in Russia in 2002), led to his estrangement from his father. His younger brother, Kim Jong Un, was instead heralded as “the Great Successor.”

In a 2010 interview with Japan’s Asahi TV, Kim said it was his father’s decision to name the younger Kim as the next leader, and that he was willing to help his younger brother “when he needs it from overseas.” He added that he was not interested in becoming North Korea’s next leader. “That’s good, because we don’t think he’s in the running,” TIME wrote at the time.

What happened next?

After the embarrassment of 2001, Kim took up residence in the casino mecca of Macao, where he gained notoriety for his gambling habits and hard drinking. There were rumors that he was based in the former Portuguese colony to help his family’s regime launder money through a shady web of banks and casinos. In 2007, Macau’s Banco Delta Asia agreed to dissolve all ties with North Korea after the U.S. Treasury accused the bank of acting as the country’s “willing pawn.”

Who does he leave behind?

A Chosun report in 2010 found that Kim has at least three children. The oldest, Kim Han Sol, is now thought to be in his early 20s. His online media presence — with appearances on YouTube, Facebook, MySpace and the dating site Asiafind — became an occasional hot topic in South Korean and Japanese news media, TIME reported in 2012.

The same year, Kim Han Sol sat down with former Finnish lawmaker Elisabeth Rehn to discuss his life and his unusual family for a televised interview. He told Rehn that he had never met his grandfather Kim Jong Il. “I was waiting for him until before he passed away, hoping that he will come find me,” he said. “I really didn’t know that he knew that I existed.”

Why was Kim Jong Nam killed?

The specific details are unclear, but this doesn’t appear to have been the first attempt on his life. According to the Daily Mail, in 2011 a North Korean agent tried to assassinate Kim in Macau, but failed after a bloody shootout with his bodyguards.

It is widely speculated that Kim Jong Un felt threatened by his older brother, who had criticized the regime from afar.

Write to Kate Samuelson at kate.samuelson@time.com.

Read More From TIME

Related Stories