The family of key Al-Qaeda figure Anwar al-Awlaqi protested Tuesday the "unbelievable" killing of the slain US-born cleric's 16-year-old son in a separate suspected US air strike.

"To kill a teenager is just unbelievable, really, and they claim that he is an Al-Qaeda militant. It's nonsense," Nasser al-Awlaqi, the boy's grandfather told the Washington Post. "They want to justify his killing, that's all."

The elder Awlaqi said his grandson had run away from the family home in Yemen to look for his father, a Yemeni-American who the United States accused of being a leader of Al-Qaeda in the Arabian Peninsula.

Anwar al-Awlaqi, who was the first US citizen to be put on a US list of militants targeted for assassination, was killed September 30 in an air strike in Yemen.

The teenager, Abderrahman al-Awlaqi, who was born in Denver and was a US citizen, was killed October 14 along with his 17-year-old Yemeni cousin in a suspected US drone strike that left nine people dead.

He was the third US citizen killed in suspected US air strikes.

Nasser al-Awlaqi told the Post that he was told by people in the area where the air strike occurred that the two teenagers were about to have a meal with a small group of men when they were hit.

"The others I just dont know. Maybe they were being targeted," Awlaqi said.

Yemen's defense ministry said last week that AQAP's Egyptian media chief Ibrahim al-Banna'a was also among the dead, describing him as wanted "internationally" for "planning attacks both inside and outside Yemen."

The Post said Nasser al-Awlaqi, who had denounced his son's killing as an execution without due process, decided to speak out after news reports described his grandson as a 21-year-old militant.

The family issued a statement urging people to visit a memorial Facebook page for Abderrahman.

"Look at his pictures, his friends, and his hobbies," the statement said. "His Facebook page shows a typical kid. A teenager who paid a hefty price for something he never did and never was."