They were among six men and one woman accused of conspiring to wage war on the United States.
Palestinian-born Maher Hawash, 39, was sentenced Monday to seven years in prison. Ahmed Bilal, 25, was sentenced to 10 years and his brother, Muhammad, 23, was sent to prison for eight years.
All were given reduced terms because they cooperated with authorities.
"I do not blame anybody else except myself," Hawash said in court. "It's something I have done that was completely out of my character."
Hawash, a former Intel software engineer, was the last of the group to be arrested. The Bilal brothers, among the original group of those arrested in October 2002, had pleaded guilty to charges of conspiring to help Al Qaeda and the Taliban and to firearms charges.
Two other men who were allied with the Bilal brothers and Hawash have already been sentenced to 18 years in prison. The federal government has said the sixth man, alleged ringleader Habis Abdulla al Saoub, 37, was killed in a shootout in Pakistan (search).
The lone woman in the group, October Lewis, was sentenced to three years in prison after she pleaded guilty to wiring money to the group to assist their efforts.