Hamza bin Laden, son of former al Qaeda leader Osama bin Laden, has married the daughter of Mohammed Atta, the chief hijacker in the 9/11 terror attacks in the United States, reported The Guardian on Monday. In an interview with the newspaper on Friday, Osama bin Laden’s half-brothers confirmed that the wedding had taken place.

“We have heard he has married the daughter of Mohammed Atta (an Egyptian national),” said Ahmad and Hassan al-Attas. “We are not sure where he is, but it could be Afghanistan.”

Hamza bin Laden is the son of Khairiah Sabar, one of Osama bin Laden’s three surviving wives. Sabar was living with her husband when he was killed in Pakistan’s Abbottabad in a military operation in 2011.

The half-brothers added that Hamza was planning to avenge the death of his father. He is considered the second-in-command to current leader Ayman al-Zawahiri in the al Qaeda. He has reportedly threatened to exact revenge against the United States for his father’s death.

In January 2017, the US added Hamza to its counter-terrorism list, prohibiting its citizens from doing business with them.

Laden’s wives and other children have gone back to Saudi Arabia, where they were given refuge by the former Crown Prince Mohammed bin Nayef, reported The Guardian. They stay in touch with Laden’s mother, Alia Ghanem.

“When we thought everyone was over this, next thing I knew was Hamza saying I am going to avenge my father,” Hassan al-Attas told the newspaper. “I don’t want to go through that again.”