North Korean leader Kim Jong-un’s eldest child might not be a son after all.

In patriarchal North Korea, the eldest son -- whose existence remains a mystery -- would naturally be the heir to the North Korean leadership. Kim’s only publicly seen child to date is Ju-ae, a girl who is believed to be around 10 to 12 years of age.

Joao Micaelo, Kim’s friend from his school days in Switzerland, told Radio Free Asia on Wednesday that he has not heard the North Korean leader speak about his children other than the already-known daughter.

In his phone call with RFA, Micaelo said he was told by Kim that he has a daughter. Kim mentioned no sons, he said. Micaelo, who went to school with Kim in Switzerland in 1998, claims he had intimate conversations with him about his wife and children during his two trips to North Korea in 2012 and 2013.

The recording of the phone call released by RFA was dubbed over in Korean.

Authorities in South Korea have given mixed assessments as to whether the North Korean leader’s firstborn is a son, or if he even has any sons.

A Ministry of Unification official told reporters at a conference on Monday that Kim may not have a son as his eldest child as previously speculated.

In March, South Korea’s National Intelligence Service briefed the Assembly that it was looking into the intelligence that the eldest child is a son, and that it was not confirmed.

At the time the NIS reported that it believes that Ju-ae is the middle child of three. Little was known about her two siblings, including their sex. Despite her high-profile appearances, she was not viewed as the successor.