"We are not convinced on the available evidence in the absence of [a] dead body," said Omar Bin Laden, 30, who said he was speaking for his many brothers.
The son, who long ago denounced his father's murderous ways, said Obama was no better than the terrorist.
"As [I] condemned our father, we now condemn the President of the United States for ordering the execution of unarmed men and women," Omar Bin Laden wrote.
The wife of one of Osama Bin Laden's couriers was killed in the May 1 raid, along with two couriers; Osama, and Osama's son Khalid.
Omar Bin Laden wrote in a statement to The New York Times that his father should have been given a fair trial and the presumption of innocence. He also griped that Osama's body was dumped at sea and not returned to the family for burial.
"We maintain that arbitrary killing is not a solution to political problems," he said.