Kim Jong-un’s friend from school says North Korean leader doesn’t have a son

South Korea’s unification ministry echoes claims that Kim may not have a son

North Korean leader Kim Jong-un, right, and his daughter, Kim Ju-ae, visit the country's aerospace agency on Tuesday (AP)

Kim Jong-un may not have fathered a son as he never mentioned a male offspring during their conversations, the North Korean dictator’s school friend Joao Micaelo said.

Mr Micaelo has long claimed that he attended school with Mr Kim in Switzerland in 1998 and made several revelations in previous interviews, including that the North Korean leader enrolled under the name Pak Un at the school.

Mr Micaelo, the son of a Portuguese immigrant couple, said he sat next to Mr Kim on the first day in class without knowing he was the son of North Korean leader Kim Jong-il.

In his latest interview with Radio Free Asia on the topic, Mr Micaelo claimed Mr Kim never mentioned his son in his intimate conversations with him about their families.

He said the North Korean leader spoke about his daughter with whom he has been seen publicly, and even his wife, but never mentioned a male offspring.

Mr Micaelo said he had intimate conversations with him during his two trips to North Korea in 2012 and 2013.

Speculation over North Korea’s successor after Mr Kim have reached a fever pitch following his much-publicised appearances with his daughter Kim Ju-ae during various important events.

The daughter, believed to be 10 to 12 years old, has been recently seen accompanying her father to missile launches, military parades, and other political events in a country with a reputation for maintaining secrecy.

North Korea is a highly patriarchal society that has been ruled by three male leaders: Kim Il-sung, his son Kim Jong-il, and his grandson Kim Jong-un. However, there has never been a female leader.

In a family where details are closely guarded, several believe that Mr Kim may have a young son who would take the father-to-son succession line.

The recording of the telephone interview with Mr Micaelo was released by RFA, dubbed in Korean.

South Korean authorities have provided conflicting assessments regarding the North Korean leader’s firstborn, including uncertainty about whether the child is a son or if he has any sons at all.

In March, South Korea’s top intelligence agency said Mr Kim could have three children and the eldest could be a male heir. The National Intelligence Service (NIS) told the parliamentary intelligence committee that it continued to believe that he has a son but does not have "concrete evidence”.

On Monday, a Ministry of Unification official told reporters that Mr Kim may not have a son as an eldest child and heir as it was speculated.

Mr Micaelo previously said that the head of the rogue state had a good sense of humour and an impressive collection of Nike trainers.

“We had a lot of fun together. He was a good guy. Lots of kids liked him. I don’t know anything about his life today. All I know is the guy I knew in school,” he told the Daily Beast.

“He loved basketball. We played a lot together. I’d like to say to him, if you ever have the time, please contact me again so we can catch up.”