He and his father watched together as the twin towers fell, and Ayres said, "Dad, I want to go fight for my country."
Years passed, and his father nearly forgot the comment. Then, one semester into college, the Malibu High School graduate quietly signed up to join the Army.
"We were shocked," recalled Nancy Schellkopf, a former teacher and family friend. "We said, 'Aren't you interested in the Navy or the Air Force?' He said, 'No.' "
Ayres' family believes that he was influenced by the experiences of his grandfathers in World War II; one was a Marine and the other worked in the Pearl Harbor shipyards when the Japanese attacked.
Ayres wanted to make a difference in the lives of Iraqis, his family said.
"He was fighting for their freedom," said his sister, Dorothy Ayres, 27.
Ayres, a 23-year-old sergeant, died Sept. 29 in Baghdad after being wounded by insurgents who attacked his unit with small-arms fire, the Department of Defense reported. He was assigned to the 3rd Squadron, 2nd Stryker Cavalry Regiment in Vilseck, Germany.
He was due home on leave Nov. 19 to celebrate Thanksgiving and planned to see family and friends and go to Disneyland.
Ayres will be honored today at an 11 a.m. ceremony at Malibu City Hall, where his sister plans to talk about how she watched her little brother evolve from a follower to a leader, shaped in many ways by his experiences in Iraq.
Ayres was born, along with a twin brother, on July 26, 1984, in Santa Monica, one day before his sister's fourth birthday. Since she and the twins had birthdays so close together, they shared one big celebration.
Their names were all inscribed on a hefty ice cream cake, she said, and, at first, it felt a little like a letdown, like having your birthday on Christmas. Then, she said, everyone grew used to it. Their mother would take them to Sea World or Raging Waters.
Ayres was mischievous and full of pranks as a boy, said his father, Robert T. Ayres Jr. "He'd climb as high as he could in a tree. He was all boy," his father said.
Ayres used to hide behind the front door when his sister came home after midnight, jumping out to scare her. But all that changed when he returned from Iraq on a visit.
"He would pay for dinners. He would open doors. He was a real gentleman. I would say, 'Where did you come from. Who are you?' " his sister said.
Ayres relished the outdoors and used to sleep on the beach. He was physically fit, even in his pre-Army days, and walked with a certain purpose, his sister said, adding, "He always looked like he had a place to be."
He was a volunteer gardener at the Los Angeles National Cemetery in Westwood, where he is now buried.
Patriotism was important to him, and his decision to enlist set him apart from many of his classmates, his sister said.
"It's not a very popular thing to do in the Malibu area," she said.
She and her father say the war that Ayres told them about was drastically different from the war being described by what they call a biased media. Ayres relayed stories of a country where U.S. troops are building schools and Iraqis are receiving improved medical care. He grew to admire the Iraqis.
Stationed in Mosul during the first of two tours in Iraq, Ayres reported that the streets were growing so safe that he could go out and play with the neighborhood children. His father began sending him cartons of stuffed toys and dolls for the children, along with DVDs and beef jerky for his son. The children nicknamed him "Soldier Bobby."
Ayres' mother, Michelle Ayres of Los Osos, Calif., said he inspired her to join the California Army National Guard. She was sworn in a few weeks after he died and wants to serve in Iraq as a psychiatric nurse.
She wonders if her son enlisted in part because he was a twin: "He was always compared to his twin, and it doesn't matter if you're in different classes, and look totally different. In the Army, Robert was his own person."
After Ayres' death, his sister received an e-mail from Chris Sanders, one of her brother's friends who also is serving in Iraq.
"I did talk to some of the guys who were there when he was hit," Sanders wrote. "When they started taking heavy fire, he pushed his men into the doorway of a house and spun around to return fire, to cover his troops as they moved.
"That's when he was hit. He died protecting the men he led. That's the way any real infantryman can hope to die.To me, that wasn't abnormal for Bob. He put his men's life before his own, all the time."
In addition to his parents and sister Dorothy, Ayres is survived by his twin brother, Jackson Ayres of Atascadero, Calif.; a brother, Aaron Mizrahi, 19, of Los Angeles; and a sister, Mimi Mizrahi, 17, of Los Osos.