EGLIN AIR FORCE BASE, Fla. (AP) — Four-year-old Ava abandons her playmates at school, flying into the arms of Air Force Sgt. Stacia Zachary. The mother and daughter head to the playground.

Their afternoon routine will change in August, when Zachary deploys to Afghanistan for six months and her husband, Air Force Sgt. Christopher Zachary, tackles the solo parenting duties for Ava and her 13-year-old half brother. Then in December, dad will deploy and the kids will go to Idaho and stay with an aunt until mom returns.

Growing numbers of American servicemen and women are married to each other — up 35 percent from 2000 to 2007 — and eight years of war that have stretched the military's resources mean deployments for both spouses can come in rapid-fire succession.

Many of those couples have children, although the Pentagon does not track that number. For the kids, it means rarely having both parents at home simultaneously. When both are gone, or when duties keep the home partner too busy, extended families often come into play. Kids head to grandparents, aunts or other relatives, sometimes across the country.

It's a unique sacrifice military families make to combine having a normal life with a state of drawn-out war. It has its own stresses and rewards, couples say.

"In a lot of ways, our children serve, too," says Stacia Zachary, a combat photographer.

For the parents, it can put added strain on marriages as they spend months apart and worry, like the kids, about a loved one on the battlefield.

"We've been married seven years, but we figured that we've spent only two and half of those together," says Christopher Zachary, who serves in the Air Force special forces.

But dual military marriages can also foster closer ties with extended family, and help sustain a solid marriage because fellow soldiers, sailors, airmen and Marines better understand the demands and culture of military life than civilian spouses, couples say.

The Zacharys were among 128,347 active duty and reserve members of the military married to other service members in 2007, the latest year for which Department of Defense statistics are available. That was a 35 percent increase since 2000, when there were 95,336 dual military couples. It does not, however, track the number of children dual military couples have.

With no end in sight to the wars, more military couples are deciding not to put off having children, said Ann Huffman, a psychology professor at Northern Arizona University who has studied dual military couples for the Army. The economy has played a role too — the military offers good paying, steady jobs, and couples are reticent to give up one income in this economic downturn, she said.

Dr. Michelle Freedman, chief of Family and Child Service at Madigan Army Medical Center's Department of Psychology in Tacoma, Wash., says the center recently saw a lot of 4 and 5 year olds with deployed parents getting kicked out of preschools. Freedman said the kids were acting out because they were upset about changes at home. The worst-case scenario for children who have too much upheaval is an inability to form an attachment to any caregiver, she said.

"But as long as a caregiver is sensitive and loving and nurturing, the children will get through the transitions pretty well. Kids are really very adaptable," she said.

Tiny Ava Zachary has saluted the American flag since before she could talk. Kyler, her 13-year-old stepbrother, worries about his dad and stepmother whenever they leave on another deployment. He's long been old enough to understand they are headed to dangerous places.

The deployments aren't easy for the Zacharys' extended family — her parents and his sister — who are helping raise the children. Stacia Zachary's father, Gary Tieman, said his granddaughter was just 10 months old the first time he cared for her at his home in Delran, New Jersey, while his daughter was away.

"But on the second deployment she was 3 and understood a lot more," Tieman said. "There were times when she just wanted to go home to Florida and be with her mom and dad and brother."

Saying goodbye to Ava when her parents returned was tough because they had grown close, he said.

Melissa Zachary, Christopher Zachary's sister, said her nephew became part of her family's routine when he moved in with her in Eagle, Idaho.

"I was really proud of how well Kyler handled the separation. He worked hard in school and helped me at home," she said.

But before his dad and stepmother returned, Zachary said she and Kyler spent a week "getting on each other's nerves."

"In my opinion (it was) both of our ways of making the separation a little easier," she said.

Dan and Maurita Blessing retired in 2007 as Navy chiefs with 24- and 23-year careers as electronic specialists. The couple had four children while on active duty.

They decided to retire and create a permanent home for the children, now ages 13 to 21, because the family was ready for stability after years of moving. And the possibility of either parent being sent on an extended dangerous deployment grew the longer they stayed in the Navy.

Chris Blessing, 21, recalls fearing for his mom's safety when he was younger.

"After 9-11, I never worried about my dad because I thought he could take care of himself. I worried a little about mom because she is our mom," he said to the laughter of his sister and brothers.

The family made it through numerous moves — to Japan, Hawaii, Florida and elsewhere — with the help of extended family and friends.

"You learn to cope and that's something I tried to teach my young sailors I supervised when they came to me with family issues," Dan Blessing said.

Air Force Sgts. Jamie and Sean Stewart and their 3- and 9-year-old sons also know the challenges of military life during wartime. In 2008, dad took the children trick-or-treating by himself and mom listened over the telephone from Iraq as her sons tore open Christmas presents.

"Deployments and war are normal topics for our family," says Jamie Stewart, a medic who has worked in emergency rooms at military hospital in Iraq and Kurdistan. "Spending time with our children is one of the sacrifices we've made to serve."

Sean Stewart says raising the children on military bases around other military families makes it easier when he or his wife head off on a lengthy deployment.

"We talked about getting out but the Air Force is our community. We are dedicated to our jobs and neither one of us wants to leave," he said.

Still, it's called a sacrifice for a reason. Stacia Zachary's eyes fill with tears when she recalls leaving Ava as an infant to attend pre-deployment training.

Later, she left for a six-month deployment to Afghanistan where she received the military's highest award for combat photography.

But when she returned, her daughter didn't recognize her. Ava had gotten used to Christopher Zachary taking to her daycare, brushing her hair, preparing her meals.

Stacia Zachary said the pain of leaving a child for deployment is overwhelming.

"It's an expectation that you are asked in this profession that you are not asked in other professions," she said.

(This version CORRECTS in 2nd graf that Ava's sibling a half brother sted stepbrother.)