Osama Bin Laden's brother has urged the former Al-Qaeda leader's son Hamza not to follow in his infamous father's foot steps.

Hamza, 29, is widely seen as a possible successor to Ayman al-Zawahiri, the Egyptian ideologue who took over Al-Qaeda after US special forces killed Osama Bin Laden in a 2011 raid in Pakistan.

After vowing to avenge his father, he has been put in charge of a highly trained group of the terrorist organisation's fighters in Afghanistan, Western officials told the The Telegraph. In a letter to his mother leaked in the media, Hamza said his 12-year-old son died a "martyr," suggesting he was killed in an airstrike or in fighting.

"We thought everyone was over this," said Hamza's uncle Hassan Bin Laden in an interview with the Guardian, referring to Osama bin Laden.

"Then the next thing I knew, Hamza was saying 'I'm going to avenge my father'... If Hamza was in front of me now I would tell him 'God guide you. Think twice about what you are doing. Don't retake the steps of your father. You are entering horrible parts of your soul."

Osama bin Laden's mother, Alia Ghanem, insisted that the Saudi-born terrorist behind the 2001 World Trade Centre and Pentagon attacks had been a good man until he was "brainwashed" in university by ideologues.

"He was a very good child until he met some people who pretty much brainwashed him in his early 20s. You can call it a cult," she said.

Al-Qaeda had never completely recovered from the death of Osama Bin Laden. His successor, Zawahiri, was seen as less charismatic, and over the past few years many jihadists abandoned the group to join Isil.

With Isil suffering heavy losses in Syria and Iraq, Al-Qaeda now hopes to woo jihadists back to its fold, and Hamza is seen as key to that effort.

He has released several audio speeches, including one in 2016 in which he vowed to avenge his father's death. He has also called for attacks on Jews and Westerners, in an attempt to keep his organisation relevant to jihadists attracted to Isil.

Isil had split from Al-Qaeda and declared its leader Abu Bakr Al-Baghdadi "caliph" of the territories it seized across Syria and Iraq in 2014, attracting thousands of jihadists to its ranks. It also fought Al-Qaeda's affiliate in Syria and Yemen.

It has since lost most of its territory in Iraq and Syria, and many of its members have been killed or captured.