Aaron Toppen of Illinois and Justin Helton of Ohio are among the five American soldiers who died in a friendly fire incident in Afghanistan Tuesday.
Military officials notified the men's relatives of their deaths in the middle of the night.
"Our thoughts and prayers are with the families of these fallen," Pentagon press secretary, Rear Adm. John Kirby, said in a statement.
Special Operations Forces and Afghan troops were on patrol Tuesday in a southern province near the border with Pakistan when they were ambushed by the Taliban.
Under heavy fire, the team called for U.S. air support, but a miscommunication led to the airstrike coming too close to the troops, killing five Americans and one Afghan soldier.
Those left behind grieved the loss of their loved ones.
"Aaron was predisposed to serve. He was very keen to be in the military," Toppen's uncle Jack Winter said of his 19-year-old nephew. "He was quite proud to be there."
Mindy Helton remembered her 25-year-old cousin Justin being "full off life."
"He was a great boy…outgoing," she said. "He loved hunting and the outdoors."
The remaining casualties from Tuesday's friendly fire tragedy have not yet been identified.
The tragedy is the worst friendly fire incident in the 14-year Afghan war and comes just days after President Barack Obama announced a phased drawdown of U.S. forces there.
All American troops are scheduled to be withdrawn from the war-torn country by the end of this year.